I imagine it has a lot to do with your mum and possibly the girls you knew as a child. I'm pretty much the opposite of you, yet my relationship with my mother was also poor, since I find it difficult to trust guys (offline anyway).
Bitchy girls, huh? I think you get most of those in school and work and it's easy to tell which ones are bitchy before you know them long enough to become friends, don't waste time with the ones like that. There are plenty of sweet and kind girls out there who won't go behind your back.