Please don't think that your post is out of norm or should not be talked about. It is a fact of life. Sex is a healthy part of the relationship between a husband and a wife. I am 47 y/o and have had Parkinson's for 17 yrs. Just checking out the other forums this morning. My girlfriend and future wife is 51. She was a virgin when we met. YES, I do know that for a fact. Whenever I get overwhelmed or doubtful about my ability to keep her should I become more incapacitated she reassures me that our relationship is not about sex. I know that she loves me. When we really get to wanting to do the deed I have to get a viagra pill, costs about 40 bucks so that's the price we pay to play. The rest of the time I simply give her lots of pleasure, attention, hugs and kisses. Works for us. I am sorry that I cannot offer you much help with your problem.
On another note have you seen the posting about stem cell transplant for MS. Done at Northwestern in Chicago, IL? If there is any way to get in there GO!!!!!
Good luck and God Bless.

https://www.facebook.com/heathernicoleHSCT?fref=nf