In what ways are you "trying to improve the relationship?"
If she is having an affair, and YOU know that she's in contact with him, and SHE knows that YOU know, and then she sees you doing things that DB would consider "pursuit?" Attraction killer!
HINT: You should be working on things that improve YOU right now, NOT things that improve the relationship with your wife. At least not while she's wayward. There will be plenty of time for that later, if and when she decides she wants to commit back into the marriage.