The advice that JJ posted is the best you'll ever get. Why I say that, I was in the same position as you...literally and now, even though I am still separated and getting my M back on track, the sex I had with my W prior was as unsatisfying as what you have been getting, and now, the sex I'm having with my W is as good as you are getting with OW.
You need your Beginners Mind at the moment (hope you've read DR) and the rich resource of advice is right here. Suit
"It's better to have no spouse than have a bad spouse"
