Welcome to SI and sorry that infidelity has become a part of your life, and sorry that your son found out the way he did. There are some posts pinned to the top of the forum that we encourage new members to read. There are some unpinned posts with bull's eye icons that are good, too. The Healing Library is at the top of the site and has a bunch of excellent resources.
If you can, IC (individual counseling) with a trauma-informed therapist can be helpful. Infidelity is trauma and your body and emotions can go haywire for a while. Please get tested for STDs/STIs, as there are some nasty diseases out there that can turn into cancer and kill you. If you're having trouble with depression or sleep, discuss with your doctor. Meds can be helpful to get you through the rough spots.
If the AP (affair partner) has a partner, please inform them so they can base their life decisions on the truth. Wouldn't you have liked somebody to let you know rather than finding out the way you did? It's the right thing to do.
You may wish to visit a barrister or several to see what D (divorce) would look like in your situation. It doesn't mean that you need to D, but it will give you knowledge.
While you're processing what has happened, you may want to evaluate what you want. Unfortunately, you won't be able to get your old life back. We're here to help you get out of infidelity, whether that's R (reconciliation) or D.
Your WH should read How to Help Your Spouse Heal From Your Affair by Linda MacDonald. Another good book is Not Just Friends by Dr. Shirley Glass. Your WH should be in IC to work on becoming a safe partner.
BW M 34years, Dday 1: March 2018, Dday 2: August 2019, D final 2/25/21