My 22 year old boyfriend does not have an interest in sex with me. We haven't even been together 6 months and he claims I satisfied him more than any of his past relationships. He was plenty physically romantic with his first strong relationship, yet his most recent before me was described as going to bed with a rock. He tells me he loves my body, tells me I am great at what I do, but he doesn't feel like being sexual. We have sex about once a month, and he makes sure I reach orgasm, but then stops. Why can't he orgasm?