The same thing happens to me too. When I'm around people I don't act like myself at all. My behavior tends to fall between 2 extremes. Sometimes I feel the pressure to talk a lot and fill in silences. I find myself putting on a high-pitched girly voice, saying immature things, and sometimes acting dumb just to make other people feel better. Sometimes I even talk about inappropriate topics! At the other extreme, which occurs around relatives and certain people I don't get along with, I become very quiet and refuse to cooperate. I sulk, refuse to talk, and lose interest in people around me.