I'll say one word..PORNOGRAPHY!
I had a boyfriend, who, like yours,was young and shouldn't have been having problems with having sex and it was due to a porn addiction. He was more excited by looking at porn and masturbating than having sex with me, though the relationship was new and he was super attracted to me. This problem is getting more and more pervasive in our society, especially with younger men. He quit the porn and now our relationship is fabulous and we have sex all the time. He says that it is the best sex of his life.
It sounds like your man has a few other psyshological troubles too and like mine, has insecurities but the porn does not help. They call it the crack cocaine of the internet. It is addictive as there are constantly new images on the net and more and more to see (unlike the old fashioned mag). A real woman can hardly compete. My boyfriend would kiss me and hug me but go home at night and masturbate to porn and never have sex with me at all. He was quite defensive about it. After he quit, there was an adjustment period and now the sex is amazing....after years together! He can't keep his hands off me and says that all those years (from age 11 or so) watching pornography on the net, had a huge effect on erectile dysfunction with normal sex.
Maybe ask him if he is willing to try quitting it for you? It is a need that a lot of young men have and he may be defensive, as it is so common now and hardly even acknowledged in our society, though more and more people are starting to have problems with addiction to it.
My boyfriend's problem was EXACTLY the same in nature...a guy of this age should not be having erectile dysfunction...viagra is NOT the answer....quitting porn is!