While I have never been into looking at porn, I don’t think you are doing anything wrong by doing so. As for your fantasies, I also have sexual thoughts that I’m not too comfortable with, some also involving abuse. Also I have a tendency to act impulsively and in doing so have put myself in dangerous situations in the past. I totally understand your feelings of being somehow less than everyone else, but for me it’s a bit more like I’m don’t belong here, like the world is a party and I’m and uninvited guest, with everyone looking at me and thinking “what is she doing here?”
I don’t think anyone can control what tends to arouse us, but we can (well most people most of the time) what we do. I don’t think you have anything to feel bad about, you haven’t done anything wrong.