My boyfriend cant maintain an !?

I had with my boyfriend for the first time the other night (not the actual first time for either of us though, just us together) and in the middle of he lost his . We were switching positions and he just lost it. We started kissing and then it came back, but when we started again the same thing happened a little while later. I dont know what could possibly be the problem! We are both young and he shouldnt be having erectile problems. Im worried its either a) a health issue or b) a psychological issue. Has anyone ever experienced an issue like this in a young man? Im afraid to really broach the subject with him because I dont want to hurt his pride or anything like that...