First of all, I've always said it would be really intersting to give everyone a honesty pill, the world would be a lot different. You are on a forum where no one knows you, so you can be honest, honesty should never be punished, so don't think that this only happens to you. Many men would admit to doing some of the things you are doing if society wasn't so infactuated by lying about same sex tendancies.
You are also young and your curiousity runs wild, that's normal and natural. You probably know more than anyone else if you are BI or not. I've heard of guys recieving oral, and their woman partner inserted her finger in the guy. Some guys love it, while it freaks others out and they hate it.
Dr. Ruth says to never live out your fantasies, because they never live up to the expectation. This is a personal thing for you. You can't fully control what your mind thinks, especially during sex. If you honestly don't think you are attracted to guys, don't fantasize about oral with guys, you probably just like the pleasure you get by stimulating your prostate. Although I would not be surprised if one day curiousity (and maybe alcohol) gets the best of you and you experiment.