Help!! Cumming too quick

My boyfriend and I have been together for some time now and have had sex multiple times, however, recently he’s been getting off way too soon, and he knows it! We’d usually be able to last 45min to an hour but now it can’t go past 5 minutes. He says it just comes out at this point whereas before, he’d be able to tell. He’s getting really bummed out by this and is now trying to avoid sex all together because he believes he has a problem. I constantly reassure him that it doesn’t bother me because he doesn’t take that long to get hard again and satisfies me before we actually get to the sex but I fear that now he doesn’t enjoy it due to him cunning so quickly. Keep in mind we’re both college students and i try telling him that maybe he’s just stressed or he has too much on his mind but he disagrees. Is there anything I could do to help him feel better about this situation or anything he can do so he he situation might change back to how it was before. Help!! I’m desperate and I fear that the lack of intimacy will eventually lead us to separating.