I think your sexual fetish has been developed and instilled upon your mind. The only way to get rid of it could be with the aid of a psychologist or psychiatrist. Until then, watch lots of heavy metal bands head bang it out and enjoy the pleasure you get from it.
Another option is... You're going to have to cut out head banging all together if you really want to get rid of it, don't watch metal bands, and don't watch head bangers. If it get's too intense, close your eyes! Eventually your mind will forget about your strange sexual fetish.
I can't really help you out with most of your troubles, but I can say, that if you are physically attracted to both men and women, then you could just be bisexual. And there is nothing wrong with being bisexual, so don't think you have some other problem on top of your actual sexual intimacy issues.