I was thinking about you tonight. I remembered something I read about Madonna-Whore complex. Have you heard of it? It's a phenomenon where the husband stops desiring his wife, who he sees as a saint and who he admires, and starts to desire beautiful women who he doesn't respect. I remember seeing that your husband cheated with a younger woman (guess what, mine's now with a nurse 14 years younger than me!) and wonder if this is relevant to you? Maybe your husband stopped desiring you at some subconscious level even though I'm sure you're better and more beautiful than any other woman he could have.
I hope you're making progress with figuring out the next steps. I guess we'll both go through divorce at the same time.