I experience feelings similar to this. I commute a lot, in my car mainly, and when anyone is behind me I try to get away from them. I think they'll ram into my car, or do something crazy. When I'm walking/jogging (trying to be healthy, just started) I freak out because I think people are staring at my disgusting body (even though I'm not deformed, overweight - im just average joe i guess). Not to mention that the park I go to to walk around - it's about a half hour away from where I live because I refuse to go to the park 2 min away from my house because I DO NOT want to see anyone i know. When it comes down to seeing ppl I already know, I go WAY out of my way to get away. I don't like the main roads anywhere, i take all back roads to and from work and school.
Idk.. I think it's a mixture of a hectic atmosphere, feeling like im not understood, a superficial relationship with my parents, and everything else negative that comes my way that other people have to deal with on a regular basis.
But, my boyfriend notices me - when I'm sitting regularly, I sit all tensed up - i never sit still - always worry - and if i have a brief moment to sit and think alone, i somehow end up crying to myself from negative thinking that doesn't ever seem to go away.
I'm sorry if this doesn't help. :-/