Can’t orgasm with my boyfriend?

I’ve had a serious boyfriend for 2 years. Everything about our relationship is wonderful and I even think he’s about to propose soon.

Except for the fact that every time we have sex I can’t orgasm. He’s the only one I’ve ever slept with. We’ve tried new foreplay and different things and nothing works. When I masturbate alone I can finish, multiple times. He does turn me on and everything too, so I don’t know what’s wrong with me. 😞 Last night he went down on me for over 30 minutes and I could feel myself getting close but never finishing. I was in tears afterwards because I was so frustrated. Anyone have any tips?