So my boyfriend is 19, and he and I have tried to have sex a couple times, but he can't ever seem to keep his erection. He has no problem doing so when he's receiving oral sex, but when it comes to having intercourse, he can never get it to stay up. He's also admitted to me, very shamefully that he suffers from very mild sadism and fetishism. Do you think his erectile dysfunction has to do with these psychological problems, or are they more physiological?