One symptom of MS can be anorgasmy--the inability to orgasm. Even if he doesn't have full-blown anorgasmy, the nerve damage associated with MS can cause noticeable loss of sensation in various parts of the body--including the sex organs. This can definitely lead to a loss of sex drive and it can feed on itself. If he feels he is not satisfying you, he may consider himself a failure in that arena and not want to do it. My advice...let him know he can/does satisfy you. If he feels he is giving you pleasure, he will want to keep doing it, even if he is not climaxing himself.