So I'm gonna tell you a story.

A couple of years ago I was with a wonderful person. For a long time we had a great sex life. But then they started losing erections and were sometimes unable to get hard. I didn't understand what was wrong. I know they wanted me because they said they did, and because for a long time we did have good sex. I was like you. There must be some reason, I though. I asked them what it was but they didn't know. That's what they said over and over: they didn't know.

I couldn't accept that. How can anyone not know the cause of something like that? It took me time but I realized I was committing the Usual Error: not everyone is like me. Some people are not as introspective. Some people don't know their bodies as well. Not everyone knows what's going on at all times.

So I stopped asking this person why because I knew it was stressing them out, and I just let things chill. We didn't have sex for a while because I know they were feeling so much anxiety over pleasing me and not disappointing me that it only made the situation worse.

And things got better.

If I were you I'd stop trying to get your boyfriend to figure out what's going on. It's probably stressing him out more because he knows you're unhappy. Give him time. He's young and healthy so things will probably go back to normal soon enough.