You need to get strong enough to set and enforce boundaries concerning the OW.
Have you done this?
Puppy
I have.. this has been THE problem..I will work through our marriage and try my hardest to do what it takes but I will NOT have another person in this marriage. it's like he was/is addicted to this girl. he will tell me that he would end things with her but then I'd find out that he'd emailed or IMd her..
And what were the consequences of that violation of your boundary?