subandi--just an idea, not necessarily a suggestion. If he thinks you only want sex, and he isn't interested in keeping up with you, would he be willing to have an open relationship? Maybe letting you find what you need/want elsewhere? This can be touchy, and doesn't work for everyone, but if the rest of the marriage is strong and something you both want to keep, this might be one way.
When I started with my lover/Master, my husband didn't know right away-I was out of state and wanted to talk to him in person-but I did talk to him when I got home. I suffer from pretty bad depression; when he saw how happy my l/M made me, he agreed. Dog has even been to our home, more than once, and everyone was very civilized. Sometimes I wish I could have both of them at once; I'm not sure we are that far, though. Still, nice fantasy, right?
Anyway, I hope you find your answer. I know this is a great place to go for advice and help.