Homicidal Thoughts, please help me!!!!!!! I don't want to think this way anymore!?

Ive been feeling this way since I was 11 and I am now 14. I'm female and I wasn't usually an aggressive or violent person. When I was 11 I was ually hared/aulted and sodomized. Ever since that day I have been very insecure and anti-social, I couldn't even hug my own dad for a few weeks because I was so traumatized. I didn't get any help until early this year. But my psychiatrist doesn't know about these thoughts. I've been looking up a lot of gore and pictures of dead bodies. And lately I've been having dreams of me killing the boy that d me in the most inhumane methods. Whenever I wake (This is embarring) But I derive ual pleasure from those images of me killing him. He goes to the same high school as me. I haven't told anyone what he did to me. One day I brang a knife to school, intending to kill him. I brought the knife to school for 3 days and on the third day I was behind him, I reached for the knife but I didn't do it. There were to many people around so I stopped myself, but the voices (as mentioned in my last question) tell me to do it, I become frustrated and then begin to hyperventilate and black out. I don't want to think this way but I hate him so much. Help me please...