My mom always puts me down?

I don't know what to do. Me and my mom fight constantly and she's says something mean to me everyday. I'm not exaggerating. She always hurts my feelings by telling me I'm fat and she always makes fun of my nose. She knows I'm self conscious, and she knows how to get to me. I'm not gonna lie, I'm rude to her a lot because after she's mean to me I can't control what I say, whenever I try to say calm and rationlize with her she tells me I'm acting stuck up. I'm not an only child but she tells me I'm her devil child and that she hates me, if any of my other brothers or sisters said any of the stuff I said to her she would just let it go and apologize to them for whatever she said. I can't stand it anymore. I'm 14 and I shouldn"t have to feel the way I do on a daily basis, I'm always a push over when it comes to my friends and they're always telling me i'm in such a good mood when all I ever fel like doing is screaming. I need help, I really want better relationshp with my mom, but she acts like a teenager and we clash all the time.