Why am I aroused by unusual people?

My girlfriend and I were talking one day about some...strange stuff to say the least. We broke up and got back together so many times, it's ridicules. Anyway, she asked me who I was with when we were broken up and if my "sexuality" changed. I told her I was with this crazy, very unusual woman and I had to ask what she meant by "sexuality". She asked if I was still straight, gay or bisexual. I told her definitely not gay but as far as bisexual that's hard for me to answer. I love women but I like transsexuals too. I mean their anatomy is so unusual, I find it erotic or arousing. I have a hard time trying to understand why that is? I can't help that I'm attracted to crazy women or that I like transsexuals. And you know my girlfriend said something about all this but that's a totally different story. So all in all, Why do these things arouse me?