Letting go of polluting thoughts so I dont lose her

A failed marriage of 13 years is damaging a wonderful relationship because I cant forget the methods used to cheat on me. Constantly feeling like I have to check up on her. As far as I know she hasn't done anything. Lot more to this.. just looking for advice on how to lose or bury baggage before it destroys the relationship. Please feel free to ask questions and or suggestions I'm at a loss and desperate for help.