Andy Hughes has given excellent advice, I couldnt have said it better! The male sex drive can be a very strange thing, it can be driven or killed off in a single stroke sometimes. There are medications out there to help his sex drive (if that is the answer) , I think a visit to a GP or therapist would be a great help, please be careful on how you approach this situation with him, if it is an issue he has with sex and i suspect he doesnt know what the problem is himself, the wrong approach could just make him even more secretive and make the problem worse. You sound like you are willing to stick by him through this, please be patient and try to understand that this could be an issue that is very deep rooted, This probably hurts him as much as its hurting you, not all us men can just flick a switch and get horny like all the Macho men out there would lead you to believe!! I bet he wants to satisfy you as much as you want him to. Good luck and dont give up on him yet, I think this can be resolved.