Talk to your DM, ask them to support you

The problem right now is that your players are clearly getting upset that, at least from their perspective, you're a misbehaving player. That's not strictly your fault: your DM has possessed your character, and is forcing them to misbehave. But the players don't know this, and it sounds like they've misinterpreted your attempts to convey this mechanical impact as an extra-diegetic behavioral change on your part. In essence, they've mistakenly come to the conclusion that you're behaving with My Guy Syndrome.

You need your DM to reassure the players that you're properly role-playing your character for the circumstances they are in.

Your DM should consider abandoning the "Surprise Factor" of the possession

If your players remain unconvinced that you're role-playing your character correctly, or are unwilling to play a game where one of their players is actively sabotaging them, then the DM should directly reveal, either through some kind of Deus-ex-GM move or out-of-character, that your character has been possessed, causing them to act weird. Character surprises like this need to be handled delicately, and from the way you've described the situation, it sounds like your DM didn't handle this situation correctly; it might be best to just cut their losses at this point, instead of dragging out the situation to whatever conclusion they were planning and further angering your fellow players in the process.

Tell the Players!

Your DM is making a mistake by hiding that you're possessed, and it's causing trouble for you, and, I suspect, causing the opposite effect of what they want.

The first part is obvious: the DM has put you in a position to do some cool roleplaying, but the rest of the party wasn't ready for this kind of thing to happen.
Campaigns where a character's actions might be influenced by things other than normal roleplaying need to establish this, in my experience. I DMed Out of the Abyss, which plays largely with the madness mechanic, and caused my players to develop all sorts of fun and weird quirks and flaws. But, I warned them that this might happen beforehand. The characters were unaware, but the players really enjoyed it.

The DM needs to stand up for you and explain what has happened, to preserve the peace, if nothing else. This will require everyone to properly commit to not metagaming off this information, but that should be standard at any table anyway.

The second part, though, is where I finally put my liberal arts degree to good use. The DM is going for surprise, but they're doing so at the expense of suspense. Alfred Hitchcock said it best in an interview with French film critic, François Truffaut:

There is a distinct difference between "suspense" and "surprise," and yet many pictures continually confuse the two. I'll explain what I mean.

We are now having a very innocent little chat. Let's suppose that there is a bomb underneath this table between us. Nothing happens, and then all of a sudden, "Boom!" There is an explosion. The public is surprised, but prior to this surprise, it has seen an absolutely ordinary scene, of no special consequence. Now, let us take a suspense situation. The bomb is underneath the table and the public knows it, probably because they have seen the anarchist place it there. The public is aware the bomb is going to explode at one o'clock and there is a clock in the decor. The public can see that it is a quarter to one. In these conditions, the same innocuous conversation becomes fascinating because the public is participating in the scene. The audience is longing to warn the characters on the screen: "You shouldn't be talking about such trivial matters. There is a bomb beneath you and it is about to explode!"

In the first case we have given the public fifteen seconds of surprise at the moment of the explosion. In the second we have provided them with fifteen minutes of suspense. The conclusion is that whenever possible the public must be informed. Except when the surprise is a twist, that is, when the unexpected ending is, in itself, the highlight of the story.

If the rest of the players know that there is a bomb under the table (a possessed party member), it gives everyone the chance to flex their roleplaying muscles, and can create some excellent suspense, instead of just a brief "gotcha!" moment, after however long the party spends being annoyed with you.

A Quick Caveat

All of this assumes that your table has a focus on collaborative storytelling rather than a curated, DM-told story. This will involve a lot of effort from everyone, but if everyone is willing to do it, I think this could be a really exciting twist.

What Can You Do?

Well, not a ton, if your DM isn't willing to listen. I'd send them the quote from Hitchcock, since he's got a bit more authority than me, a random poster with a Garfield icon. I'd emphasize the discord this is causing between the players, and that this tension may be hard to resolve. Send them a link to the problem-players tag on here, if they don't believe you; if there's no in-game explanation for this behavior, the number one piece of advice is to talk to the player, then have them leave. (Or advising the annoyed player to leave, if the DM won't deal with it.) You're not doing anything wrong, but the way it's perceived by your fellow players isn't going to end well. The party should feel betrayed by this, not the players.

Your DM has put you in a bad spot and only they can fix it

Your DM has controlled your character and made you do things you normally wouldn't and that is causing friction in the party. The DM has told you that you are not allowed to tell the party anything about it. If you decide to follow this instruction your only way to get help is through the DM herself.

Talk to your DM again and make it clear that the position they are putting you in is bad for you as a person, and is putting significant friction between you and the other players.

The only real options for the DM are to drop hints or outright tell the party what is going on with your player or to just escalate/abandon the surprise reveal entirely.

DM should start by directly addressing the issue without revealing too much of the twist

Talk to your DM and be clear that you are very uncomfortable with the real-life consequences of her actions are for you. Ask her to please take the pressure off of you by telling the other players that you are doing this for a reason. For example, she could say "[Other players], please do not blame PiousVenom for their character's actions. I promise you that they are not doing it to spite the party and that there is a very good reason they are doing it." If that doesn't alleviate the issue then the DM should just straight-up tell the others what is going on.

If that doesn't work, the DM should tell the other players explicitly

If the players still aren't satisfied with that explanation, and are still upset with you as a player then the DM needs to just come out and tell people what is going on. Keeping a surprise is not worth causing interpersonal issues at the table and no story twist is worth putting one of your players through the wringer beyond what they are comfortable with. Thus, the DM should just tell the players that you are possessed, but ask them to please keep that information out of the game and to play as if they did not know.

DM could also accelerate the pace of the reveal

This is not a great option, but if the DM refuses to do either of the two above, it is better than nothing. The DM obviously has some sort of plan for this possession and presumably intends for it to be revealed to the other players at some point. You can request that they accelerate whatever plan they have so that the consequences on your are minimized and you don't have to be in this position for as long.

Talking is the most important thing for you to do

No matter what your DM decides, talk with them and then keep talking. If they decide something and it ends up not helping, talk with them again and ask them to try something else. Don't let it go until your issue is resolved and give them honest feedback.

At the very least, once the reveal happens there is no reason the players shouldn't trust you

In the case that the DM does nothing more to help you or that nothing they do helps (for whatever reason), you might be stuck in this unfortunate position for a while. However, assuming that you are able to break free eventually, the players should be understanding once you finally reveal the reason. Once they know that the DM was forcing you to do those things, any hostility they have for you should either go away or, at worst, be directed at your DM. Hopefully it doesn't come to this though.

If the players are thinking you are domineering and obnoxious, instead of just roleplaying, that's a problem. This inability to see the difference between the person and the role is a serious problem that arises in DND games, and any places where an actor plays a role. A player plays a dumb barbarian and gets treated like an idiot away from the game. A player plays a lecherous bard and suddenly gets treated like a pervert outside of the game.

What went Wrong?

This is mostly the DM's fault in this situation. Introducing suspicion and intra-party conflict is a valuable tool in storytelling and immersion, but it relies on players being familiar enough with each other to not be so immersed as to make assumptions about the players based on their characters.

Possession is also an effective tool, but it's taking away your ability to role-play how you like and risking the My Guy Syndrome. A good DM should only enforce a possession if the player is comfortable with it.

Addressing the issue

Ask the DM to address the group and remind everyone that there's a difference between the character and the player.

Apologize when your wizard does something you as a person normally wouldn't do. If you think something is a good idea, but your wizard would be against it, make it clear. You're not drawing a line between your wizard pre- and post-possession, you're drawing a line between you and your wizard.

You might look into talking with your DM about making a wisdom save at certain points to potentially send hints that you're not fully in control. Drawing symbols in your sleep, or fill a diary with the name of the spirit possessing you. Random nosebleeds or bloodshot eyes. Animals could get scared by you. There's plenty of movies about people being possessed and acting funny. Take some inspiration and work with your DM.

Maybe when your character is raised from zero HP, or enters a church, or some other spiritual situation, you can make a wisdom saving throw to give a less subtle hint. The person nearest you could make a perception check to see a flash of shadowy aura, or get a flash of a different face over yours, or you're constantly whispering the name of the spirit.

You character is now an NPC

I can't tell them about the possession at the request of the DM.

If those are the conditions the DM has set, then you need to turn the character over to the DM and roll up another one.

Propose the above course of action to the DM. If they balk, then ask the DM point blank - "How long is this possession to last?" If the answer is that it is for a short time (a session or two), you can try to hang in there. When the reveal comes, it may come as a surprise and be fun for the other players. The DM may (and should) provide a clue for the other players next session.

If the answer is not a finite / brief time, then turn the PC over to the DM since it is now either a NPC or a GMPC. You are no longer in charge of the PC. Apparently, your fellow players are too thick to see what is going on, thus your fun suffers.

Roll up another character.

Sometimes, you have to call someone else's bluff. This seems to be such a time as regards your DM unless the DM has a plan for timely resolution of this awkward situation. That your fellow players do not 'get' what it is that is going on isn't something you can solve, if you are to accept your DM's guidance, and you have found out that they aren't the kind of group who will 'get' that.

This answers what to do. Are you willing to let go? You have already lost agency as a player regarding this character (unless you know it will end soon). The choice is yours.

Talking to your DM is the most important.

I agree with most given answers here.

but

Whatever justification you may have, (and here your clearly have the best one)

Using magic and opposed skill checks to manipulate other player characters will most certainly cause hostility and tension in the group.

In a way, that's what the DM just did to you - and you are "spreading the disease" by doing it to other players. If you are to continue roleplaying your new personality, I'd advise not to use game mechanics to "force" them do something they don't want to.

Curse them all you want when they don't listen to you. Exagerate your roleplay, be unbearable so that they have a chance to understand something has changed. Take a precious item and throw it down the hall you want to follow. Make it ridiculous. If you do it right, it will piss their characters, cause adversity with your character... and make the players laugh with you.

But don't remove your fellow players their free will with game mechanics. This most often brings tension between players, and that's what you want to avoid.

I agree with @KorvinStarmast, to a point. If this possession is long turn, your character is an NPC now. You are no longer guiding the character, but just following the DMs agenda.

If it's short term, then it should not be an issue. But, there should be some hint that your character is "off" or "not himself". Something subtle, but enough for the others to see something is wrong. If such hints are there, any good player will pick up on it and see your not being a jerk, but furthering the plot.

Talk to your DM and explain that the the players should not be completely in the dark, allowing them to discover that something is driving your character this way. Could make for some interesting role play.

Just like the problem that you're having, the answer to your situation lies in role-play

It sounds like your character, in-character, knows about the possession since it happened to them... did the DM explicitly say that your character is not aware of the possession, or did the DM say that you shouldn't tell the other players out of character? Huge difference.

What I'm trying to say is, that if you're already role-playing your character in a dramatically different way for the purposes of this possession, then would it not be in-character to tell the other PCs that you "Went out 2 weeks ago, and this weird guy cast some kind of crazy spell on me. I don't know what happened, but I feel different." allowing them an opportunity to explore what has happened to you?

It seems very strange that your other players didn't notice that your character is ... out of character. If you'd never cast hostile spells on your party before, or been in an argument with them, and then suddenly you're casting charm person; it's VERY strange that people wouldn't just say "hey Dave, are you feeling alright, you're acting strange".

To me it suggests that either:

1. your players are not used to role-playing, but dungeon crawling and killing anything they find. There is a big difference between the 2; not all DM's are good at the former as it takes a lot more subtlety and preparation; and not all players are interested in the former as it requires more effort.




2. your DM did it too early in the game - and didn't allow your players to get to know each other ... you can't suggest someone is acting strangely if you don't know how they normally act. Possession however isn't particularly low level, so I doubt this is the case.

I disagree that you need DM support - but I would play it so out of character (and you've been given some pretty lax requirements; charm person is a very diplomatic way of asserting your will... I'd have pulled out my dagger, while walking behind them) that the others have to ask "what is wrong with you?".