For problems with girlfriends, boyfriends, husbands, wives, lovers and leavers!
Remember this though, he is guilty of nothing in the full/real/actual world, so do n`t treat him as though he has done something which he has not. However, this suggests that he is n`t satisfied sexually, perhaps not with any single partner, so there is a high probability that he`ll continue to sought multi relationships into the future. Hopefully his relationship with you is not overly preoccupied with having sex. It might be that he is with you for all of the right reasons also.