Well it appears the e-badasses are out in full force. I kind of lucked out I guess, me and my roomate get along fine. I feel bad for you, this wouldmn't be good for anyone.
While you have to stand up for yourself it might not work here. No offense, you sound like the pin-cussion type who everyone makes fun of dispite your efforts and beliefs that you don't have it coming. Well it sounds like you do have it coming. I'm not saying you deserve it, but that I expect this to happen to your type.
They sound like they aren't going to accept you know matter what. You don't fit into they're little clique so your not going to be excepted by them period.
You've got to learn how to play their game. I know what your talking about, it sounds exactly like me around junior high and before that. I don't get picked on anymore because I'm not that victim anymore, and it has nothing to do with size I'm 140. I can't really describe what you need to do. For example you may think your insulting them back but to most it would come off as pathetic. They're may be nothing you can do, they're impression of you may already be ingrained; all attempts to "play their game" would come of as again, pathetic and likely funny as hell.
I'd say get out of there until you figure this out.
Sounds like you need a mix of confidence (know that your better than them), assertivness, and a sense of humor. You have to grow up before you can really deal with people who haven't.
-oh well good luck