I found the same problem with my H - everytime we ML, I would think of them (even though theirs was not a PA, but I saw the IM's where they discussed what they would do to each other). After the almost 4 months since finding the IM's, I have been able to get over that, and don't think about it anymore. After all, he is with me, and says he loves me, and wants our M to work. So, I am trying to take him at his word.
I think you should just give it some time, Crushed. Try and refocus on you and he being together, and ignore OW, because she doesn't matter anymore, if she ever did.
Thinking of ya!
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim