21 years old is a "young adult" IMO, and he is not your therapist. I agree that the fact that he's the only one you have to talk to is not a good reason. I do think you should discuss telling him with your W first.
I also agree with KD that having your son appeal and reason with your W on your behalf is just prolonging the inevitable. If she stays for that reason how does that fix anything?
Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015
A young adult like that is going to feel a great responsibility to repair his parents' relationship, and is just inexperienced enough to think he can really help. That's a lot of stress to put on a college student, and a lot of responsibility for your marital problems if he's unable to bring your wife back. In my opinion, you should consider him more of a kid than an adult in terms of your marriage. Tell him what he needs to know, in a way that maintains as much of his family stability as you can maintain. Don't use him as a confidante.
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.
Being too busy and having too much stress can be a sure killer to intimacy. I'm not just talking about sex, but emotional closeness.
Your W found the time, however, to cheat on you. So tell me, what did she get from this OM that you were not giving her? What part of the day/night did she contact OM or spend time with him?
Sometimes, an A is some people's "escape" from reality and all life's stresses, but an A takes time out of life just as a M does.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!