Pretty messed up, need some help!?

I'm too serious, I take things too harshly, I'm mean, angry at the world, confused, messed up, vengeful, I'm too detached from things, apparently nothing gets to me, I don't get involved, but underneath things affect me more than others. I'm afraid and worry all the time. I'm this sad pathetic excuse for a girl who wants things she doesn't have the courage to get or accept. I'm not normal and I'm not happy. I don't know what to do.Sometimes I feel I've become the worst version of myself, an ice-cold *****. I go from one extreme to another, from being optimistic to pessimistic, from being very happy to incredibly sad (pretty much anything can change my mood). Between these two halves I seriously don't know who I am. I went through something traumatic and I'm very sensitive, but that was almost 10 years ago..Too many people have hurt me in the past so I think I came up with this shell, only now it's backfiring on me. I really want things to get better and to have a normal life, but how?