First of all let me say that an EA is just as or damaging than a purely PA. First of all your WH is giving emotional attention and support to someone other that his S. He is stealing time, attention, and love from you and giving it to someone else. He is absent from your marriage.
My WH was absent even when he was sitting in front of me and I was talking to him. He didn't hear me, but would laugh at whatever text he just got. This was getting worse as time went on. So I finally snagged his phone while he was in the shower and discovered very loving and explicit texts to OP. Needless to say, there was a HUGE blow up. Our first fight in 30 years.
To his credit, he immediate admitted everything, and over the next few months we had many, many frank discussions. He still refused to let her go and I didn't push him because I felt that he would resent me if I forced him. I requested NC, but I felt he had to make that decision on his own and for the good of our marriage. It didn't happen for another 15 months and a 2nd DD (he still kept up with her through FB and resumed talking a year after 1st DD.)
However, all said, we have come through it and have a better marriage than we ever did. I thoroughly understand why it happened, and what he was getting out of the relationship, which was mainly an ego booster (he is 76, I am 59 and OW is 40+). It has been a true struggle to this day to get through this. Just last night I had another major meltdown. He, again, reassured me, held me, assured me of his love, all the things that I needed. We are still a work in progress, but things are much, much better.
Still, would I do things differently now? YES. I would demand immediate NC and I would demand immediate counseling. I wouldn't struggle along for so long without talking to someone. I still have not told another soul about our troubles. This forum is the first time I have been able to tell anyone. I should have talked to a friend long before now. Not necessarily for advice, but to just be able to vent.
We are stronger than ever, we will make it. I encourage anyone to talk it out, be honest with each other, work through it. Reconciliation is possible and marriage can be better than it was!
Married 33 yrs
DD #1 6/1/12
DD #2 9/15/13