being comfortable with some sex acts doesn’t mean you have to be comfortable with all sex acts and just because you consented to doing some sexual things with a person does not mean that you have to consent to doing all sexual things with that person.
you’re 100% allowed to say “i’m comfortable doing THIS but i don’t want to do THAT”. your right to set your own sexual boundaries doesn’t only apply to just whether or not you’ll have sex with someone at all but also to what you’re willing to do with them, and even if you (or they) feel like your boundaries are “weird” or “don’t make sense” that doesn’t mean you don’t have the right to have them or that they shouldn’t be respected.