erectile dysfunction help

my boyfriend and I have been together for over 2 and a half years and probably 3/4 of our relationship he has had performance issues. He can only maintain an erection for about the first 30 seconds before he goes soft and he tries but there's no coming back from it. He does not want to see a doctor at all because he says he doesn't have ED because he's too young (26) and when I tell him otherwise that it is common and could be the issue he is in denial. He doesn't want to try any pills or anything and it's taking a toll on our relationship. Any advice on how to help him or what I can do to make him feel better? In the last year he has maybe maintained an erection 2 to 5 times enough for orgasm.