Hi massgirl,
welcome to PC. I think the clue to this problem is in this statement "He doesn't need the pills when he masturbates, only during sex". Does he look at porn while masturbating? I think this could be 2 things:

1. He has become 'desensitized to standard sex because he's used to watching more stimulating act from porn.
2. He simply used to masturbating and doesn't feel the need for sex with a partner - kind of like the lazy way to fulfill one's needs.

I've read about 'desensitization' before from watching too much porn. The fact he doesn't need pills to masturbate and come to orgasm makes me think this is the problem.