Okay. Traditional guy. Man's man. My advice is tailored specifically to that.
He's going to test you. He'll suggest maybe it should end. He might mention he's considering divorce. Maybe he'll say things like, "I should find a woman who treats me right." This kind of stuff is him voicing his internal conflict. It also serves as a test. The test is very easy to pass. In each case, you just say, "no." No, I don't want a divorce. No, I don't want you to leave. No, another woman can't have you.
Fighting to keep him makes him more secure. If he vents, just know that he has to do it and let it go. There will be good days and bad. Remind him you aren't rug-sweeping and you know things aren't normal. My own wife did this by randomly apologizing out of the blue when it hadn't even been a subject of conversation. It reminded me she knew I wasn't okay yet. Don't get discouraged.
My wife says this book helped her more than the others she read.
https://www.amazon.com/What-Makes-Love-Last-Betrayal/dp/1451608489
<em>What Makes Love Last?</em> by Gottman and Silver
You really should read this. It's a bit difficult because it's dry and academic. If you persevere you get a better understanding of what it means to be valued and validated by your spouse.
My wife felt "Helping Your Spouse..." helped far more than "Not Just Friends," but she also read a general relationship book by Gottman which covered infidelity as part of the material. I believe she thought it was good.
https://www.amazon.com/What-Makes-Love-Last-Betrayal/dp/1451608489/
IMO, she really started to get it after "Helping Your Spouse..." She was a bit in denial until then. Sort of, accidental rug-sweeping. It's like, she had to read books that told her what she was doing was in fact wrong before she realized she had started down a path that put her in a club she thought she'd never join.
There’s a Gottman book about coming back from a betrayal of this depth. I highly recommend it.
What Makes Love Last?: How to Build Trust and Avoid Betrayal https://www.amazon.com/dp/1451608489/ref=cm_sw_r_awdo_navT_a_NHAZHMH1SJ384ZAA4BW8
Funny you ask because John Gottman spent his career studying this and wrote the book, What Makes Love Last?: How to Build Trust and Avoid Betrayal. He also wrote, The Seven Principles for Making Marriage Work. Spoiler alert-they are:
1) Learning to enhance one's love maps
2) Nurturing fondness and admiration for each other
3) Turning toward each other instead of away from each other
4) Letting one's partner influence You
5) Solve the solvable problems
6) Overcoming gridlock over unsolvable ones
7) Creating shared meaning
Here's his TED talk about this titles, The Science of Love.
This will require good professional help. I suggest starting with this book.
Yes!
If you look at John Gottman's work, he basically applies the principles in that book to relationships.
http://www.amazon.com/What-Makes-Love-Last-Betrayal/dp/1451608489