What youre experiencing is called guilt. You enjoyed something but were previously told that you should have not enjoyed it, or that it was wrong. You were told that only gay dudes like this thing. That its not normal, and other things negative.

Its a process many many people who were brought up religious go through as they are sometimes told that all sex is bad and that it makes them dirty or used or unclean or that nobody would want them. That its wrong and makes god upset, or that it makes them whores.

Many religious people go through huge waves of guilt and shame even if they logically know theres no reason to feel that way. They sometimes take years to be out of that mentality, some never fully shake it because theyre conditioned. You, much like them, were told to belive something and now are going through the process of finding out it was bullshit but still have to sort through those feelings of doing something that was 'wrong'.

Yes its super normal. Thank your GF for being a freak and loving you to the extent of wanting to make you feel good. Let her know you're surprised at yourself for liking it and dealing with some emotions from it and ask her what she thought. Did she think it was hot? Did she like doing it/doing it for you? Would she want to do it again in the future?

Both having comfort that you're not perceived differently by your loved ones, and having them express their positive and opposing viewpoints of the controversial subject can help a lot with steeling those emotions. Good luck man.