First, I'd say that pleasure is pleasure and there is no shame in enjoying your body or your partner playing with it. Second, sexual pleasure doesn't determine your orientation no matter what society tell us. From what I understand (nonscientific) oral sex is more common among gay males than is anal sex, and I doubt that he feels that concern around his orientation when receiving oral from you
Plus, for some men this is a threshold that needs to be overcome. Finding out that you can truly let go sexually, be completely vulnerable and trusting of your partner in such an intimate way can be very powerful and take time to allow, that time can also serve to intensify the experience and orgasms in a positive way and the intimacy between you both. This is especially the case if he feels he can trust you, and allow your assertiveness to guide his experience....as, unlike the penis, he can't really see what you're doing down there. Total sensory experience
Good luck and enjoy I know I do.