I need help and anger management is NOT working... something is deranged about me.?

I am 27 years old and I think I'm the nicest person I know until I get crossed. I am a very simple person who takes things for what they are. I think something is wrong with me because when I have friends (I use the word very loosely) they seem to always do something to me that gets me upset and then I cut them off 100% I mean, I will tell them exactly how I feel and leave them alone. Delete phone #, e-mail addresses, smile at them if they walk by but say nothing to them. My boyfriend says I'm just evil but honestly it hurts! I try to be nice to people but when crossed... I'm the rudest person ever. Some 'friends' will apologize and I accept their apology but I still seem to keep them at a distance from fear of hurt again but I feel like this is going to (starting to) ruin my life! I guess growing up I saw the way people treat my parents and I don't give people the satisfaction. Please help! I'm honestly thinking about going to a Convent or something just to be by myself so I won’t hurt people and people won’t hurt me but I know that’s not the way to live. I have attended several Anger Management classes and I take medication (Prozac) for my depression\mood disorders which I don’t think are working anymore. When I get upset, my heart races and I get this feeling of rage in me that makes me want to fight and cuss people out, or I think about being locked up in a jail cell because I killed them. I don’t think about how I kill them, I just fast forward my thoughts and imagine myself sitting in a jail, looking at the wall, saying, why did I hurt them?! Then I snap out of it, take deep breaths, walk away and cry while thinking of vengeful things to do. Then, after those few minutes, I start to pray, then I feel better and continue my day and talk about what transpired or I give them the cold shoulder until they ask me what my problem is, and then I rail on em! Then, I feel better!!! Help!