He has rejected any physical advances from me, though, saying it is too painful for him.
It's not necessarily too late. I'm the high-libido husband in an long-term SSM, and I am no longer "attracted" to my wife specifically, even though I can clearly see that she is physically attractive. As I see it in my case, it's largely a simple matter of conditioning, or trained response. If you like ice cream and someone gives you an electric shock every time you taste it, you will eventually dislike it. At first, you will avoid it because you know you're going to get the electric shock. But eventually, after enough negative reinforcement, you actually lose your interest in that particular kind of ice cream. Whenever you see that particular ice cream in that particular setting, your mouth no longer waters. And eventually, you learn that ice cream elsewhere could still taste good, it's just that particular ice cream associated with the electric shock that you don't like.
How could my wife and I turn this situation around? It's clear in my mind that she would have to be sexually positive and encouraging, for a long time, and do so CONSISTENTLY, so that I could develop positive sexual feelings toward her again. It's emotional retraining, not intellectual knowledge. If she magically and suddenly became sexually positive, I know I'd feel negative and suspicious about what is going on, and I would be expecting sexual rejection to resume any time again. It would take weeks, or maybe months, of consistent positive physical intimacy with virtually no rejection before I'd emotionally "believe" it was real.
Of course, there are all kinds of higher-level issues involved here about love, honesty, etc. I'm only addressing a few gut-level, but very important, mechanisms here -- basic negative feelings of fear of rejection vs. positive feelings of sexual acceptance, etc.
I think consistency is very important in retraining at this level. Even after some positive experiences, even a single rejection can cause backsliding and bring back all the old feelings. You're fighting baggage you didn't have when you first met, at which point you could probably say "no" and take a raincheck once in a while without any consequences.
Anyway, that's my view of it, and your mileage may vary.
