Why wasn't I feeling it?

My bf and I had some sexy time a few times(without penetration) and I've been super turned on and enjoyed the fingering and kissing all-over. But last night, we had sex for the first time(my actually first time having sex) and I wasn't feeling as amazing. Nothing he was doing was turning me on like that. It wasn't painful and he hit the right spots a few times, but it wasn't that great. I still enjoyed the intimacy,so it wasn't like it was really bad or that he was bad. What's going on with me?