Dude! First, relax... It's all good! I'm a man in my 20's and I'll tell you, I've been turned on by all sorts of things growing up, and you know what? It hasn't really stopped being a dynamic, changing thing. Your tastes change, or they don't.... Either way, what you like is what you like and its rarely something to be ashamed of. Just don't cross the line in public, and don't offend or hurt anyone, and you are free to think about all the butts you want! That being said, when it comes to your sex drive with your girlfriend, it's probably down because of all your anxiety about your sexuality and fetishes. Assuming you are a virgin (sorry if that's not the case) that anxiety is going to be EVEN HIGHER, which makes getting an erection or being interested in sex even harder! I've had this problem with most of the women I've been with for the first time... I get nervous that I won't perform, and then I don't perform. So I'll reiterate: you need to relax! One of the best things that helped me get past this was my accepting myself for all my weird interests, and quirks, and owning the person I am! I'm not saying go around and shout that you like guys pooping - but know inside that it's not as crazy as you think it is, and everyone has their weird things about them. It's all about confidence that you are no weirder than anyone else. The best thing that happens when you really accept and own who you are is that the people who become your friends are attracted to the REAL you, and the friends who fade away, you come to find, were only around because they liked the "fake" version of you.

Sorry for the long post, but I hope this helps you! Feel free to message me if you want to chat about this more. Being young and confused about your sexuality is totally normal! Don't sweat it!