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 with the other answers saying 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?".