I wouldn't be at all surprised if that was the case. Generally speaking this is exponentially more difficult for the men to deal with than their partner. Imagine how difficult it must be for him to want to have that type of relationship but his own body is betraying him. For some reason their self worth is tied very tightly to their ability to perform.

The only way to really find out is to talk to him about it. But don't be surprised if he tries to avoid this issue like the plague. It's much easier to pretend it isn't happening than to deal with it.