Hello, and welcome.
Unfortunately, I don't have any great advice that will make this go away, but if I've learned anything from this forum, it's that if you make a big deal out of your fetish and let it rule you're mind, then, well, it will be a big deal in your life and it will rule your mind! If you accept it and realize it's just a weird part of who you are, then you'll have a much easier time dealing with it.
I don't have an incest fetish, but I do have my fair share of sexually abnormalities, so I know how you feel. And I also had an opiate addiction that I used, in part, to cover up the thoughts I have.
Plus, Sigmund Freud had that theory that, deep down, every male subconsciously wants to have sex with their mother, so maybe it's not that uncommon!