was sexually assaulted or maybe not

i was 16 and he was 19. we were drinking, together with our friends. we barely know each other, and after a couple nights of drinking together, he asked me if i were okay with sleeping with him and not make a big deal out of it. like doing it casually whenever we get together. i agreed, thinking that it would be fine, even though i had a boyfriend then. and later on, i just saw us having drunk segs. i didnt even feel any pleasure, as far as i can remember. it was just blank.

idk if this was sexual assault, since i agreed. i havent told this story to anyone. also i keep on thinking that i cheated on my (now ex) bf, so i dont think i have the rights to feel like the victim here.