According to God, cheating is a deal breaker.
When I faced this, years ago, I took it to a christian psciatrist to look over and advise. We were terrible broke at the time so percentage wise to our income it was at a huge cost, but what he said worked.
As I present the problem to him, I put aside my personal feelings about what was happening and presented it as fairly as i could from both our viewpoints, and managed to give an overall picture as fairly as I could of who we both were in as few words as possible. I was up front that working with the psyciatrist in a long healing process was out.
To show you how simple a solution can be, here is mine. Every person is different, our solution wouldn't be yours. Our basic probolem was in how my husband saw himself in relation to my spending more years in school than he did, and my out talking him. He had accomplished so much and was so smart I hadn't a clue without being told by a professional.