He won't cum in me

Me and my boyfriend have been having sex for about two months now and he's never been able to cum when he's inside me. There's been a few ocassions when he was close but I usually have to finish him off with my hand or my mouth or both :p and it's got me wondering if something's wrong ? He's extremely fit and says its "stamina" but I'm not sure. Thoughts please ?? 💕
Edit: we always use condoms. What I meant was that he can't orgasm while he's in me.