What has been most helpful on this forum (and similar sources) has been just reading without posting. It has given me a better perspective on my situation.
It has taken me quite a while to really fully understand that many people have low desire, both mentally and physically. I've never experienced anything but high desire my whole life, with lots of fantasies and physical desire. I thought that the biggest problem anybody could have was trying to contain one's desire, not to get aroused when you didn't want to. It wasn't until I heard about Viagra, which was also around the time my wife lost interest, that I realized that there are many people who don't feel automatic desire, and don't fantasize, or can't get aroused. I now realize, for example, that's what happened to my wife is not that unusual. Well, that helps. It's better than thinking there's something seriously wrong with her or that it's because she's trying to frustrate me.
What am I going to do, etc.? If I knew, I'd be doing it and not posting here.