My boyfriend and I have been having sex for a few months now and we've never had any problems or concerns with either of us. Recently if he's thinking about something else during sex or concentrating too much on trying to please me and his mind strays, he can't get an erection again. He can have an erection the first time but after that he's now encountering problems. He's 34. Is there any medical reason that this could be happening to him?