What is wrong with me? Serious answers please!!?

I am a very good person. I am not violent. I don't kill bugs. I appreciate nature. I am selfless. I am sympathetic. I am caring. I am loving. BUT.. for the past couple years, I noticed my mind is very sick. I am awed by serial killers, catastrophe, natural disasters, m deaths, torture movies, gore, and just basically anything sick and evil. I am obsessed with dark, and evil things. I am not a satanist, but I find satanism awesome. I like Anton LaVey. When I hear of horrible and sick things happening, my reaction is "AWESOME", and I find it exciting. I'm confused because I would never do any of those things, but I find myself excited by them. When I say excited, i don't mean ually. Keep in mind I'm also the person that wants to join the Peace Corps. This makes absolutely no sense to me. I have such sick thoughts in my head, and I say them jokingly around my friends, and they drop their jaws and say i'm terrible, but they know me, and know I wouldn't do these things. Is there really such thing as being possessed? What has happened to my mind? Should I be alarmed? Is this normal? I feel like a half of me has been corrupted, or something hijacked my mind. I do have Bipolar disorder, and I am not medicated, but I doubt this has anything to do with it.. Help!