It may be less of a sexual obession that some type of "penis envy." So I read it more as a masculinity issue. Not sure how to advise or help, but I can say that I get it, to some degree. For me, though, it becomes an issue of measuring up in the face of sex with me, as I am a gay man. But I think that all men can share in masculinity issues, to some degree, based on their own situations, lives, and desires.