advice on coming out

hi just looking for some advice :)

i (F) recently had sex for the first time. me and my boyfriend have been dating for a while now, but ive always been very uninterested in sex. ive never had the desire for it, and ive never felt sexually attracted to people, so i have felt as though i might be asexual for a while. i thought that might change after getting into a relationship but it didn’t. i decided to have sex anyway as i figured it would be useful to gage how i felt (wether id enjoy it, wether id feel comfortable etc) but i didn’t like it. let me make it clear that everything was fully consensual! 

people say the first time is never good, but i don’t really want to try again, simply because i don’t have the desire for it. it has solidified by belief that i am asexual. i haven’t spoken to my boyfriend about it yet, and im not sure how to go about it.

have other asexual people had this experience? how have you dealt this it in your relationships? does being in a relationship with someone who isn’t asexual work?