There has to be something you can do that can turn him on. I think it just may take some work but hopefully you will find success.
Masturbation gets talked about quite a bit on this forum, to me there is no substitute to making love to a woman, I suggest you ask your partner to leave himself alone for a while to see if that helps.
Looking at it from another point of view the problem may be in your partners head, I remember taking two weeks to achieve an oirgasm inside a woman when I first met her, I guess I was used to my previous partner, eventually we resorted to extreme measures, there were guys working in the street outside our bedroom window, we opened the curtains and I reached an orgasm in just a couple of minutes, no the guys could not see us but just the notion that they could was enough to do the job, why am I telling you this? I guess there are things that can go on in a persons head that can interfere with his sex organs.
I had this problem with every new partner I had, I could never have a one night stand, it would have been a total waste of time.
Depending how much a lot is, yes it could make a difference. Particularly depending on how good his physical condition is.