[help] does my boyfriend need help?

Hi guys, I'm 27 he's 20, we've been together for a year and a half now and I love him and want to spend the rest of my life with him, and I truly believe that he does too. He was a virgin when we started seeing each other, and he was a top in our first adventures, but in a month or two he started to want to bottom and he loved it, and so do I. Ever since that moment he bottoms and I top, no problem, but sometimes we want to change. The problem is that soon after he started bottoming, he can't seem to hold an erection, he can get hard but most of the time if he stops masturbating, it will get down again. This didn't happen at first and now every time he tries and it doesn't work out, he gets super depressed and anxious so I think he is only making it worse. I told him to let it go and that it's no problem and that he should not think about it but sometimes it gets frustrating for me also. What should I do? I asked him if he wants to see a doctor because I don't think this is normal for his age, but he is super embarrassed about it.This happens in all situations, including watching porn, so I don't think it has anything to do with physical attraction regarding me (though I've thought about it) since he can easily get hard, just not maintaining.Also, the few times he was able to top (with a cock ring) it was very hard for me, because of almost no bottoming in the last year and a half and also because his dick is thick as bends to the side, which is painful in every position I know of. Any suggestions on positions for side bended dicks?Sorry for the long post and thank you all!