The problem with the sex is most likely completely emotional. He was just fine having plenty of sex with you not too long ago - so don't worry about the whole kegel thing (not that it could hurt).
I'd mentioned previously also that you should make sure that you both get checked for diseases and such. With OW's history, you really should do that soon (just in case).
Things sound like they are getting better, so hopefully he stays away from her this time.
