I'm far from an expert and certainly have my own issues related to intimacy, but having said that...it sounds to me as if you're having panic attacks when things become intimate. Which is very understandable considering the very recent A and all that comes with it. If they go back awhile, as you've described, there may be another issue (and I don't know what that is) at the root of it. But it certainly sounds as if it was made worse with the affair.
I don't know if that helps or is so glaringly obvious that it may sound insulting--I don't mean it to be. But maybe if you can give those things some thought some lights may come on in your head. Good luck, and congratulations on piecing.
M60 H52 D20 M14 yrs OW-old gf from 1986 bomb-5/18/08 H filed for D-9/10/08 D final 4/24/09 xH remarried (not OW) 2012