Oh honey, I'm sorry. I have some idea how this hurts. In my case, ex slept with an old flame the night before we married, spent the next 6 mos writing to her until I found out. I'll spare you all the details, but many years of apparently good marriage, three kid, then an affair after 16 years of marriage. DB'd my tushie off, great reconciliation, then full MLC and divorce at 24 year mark.
My point? Even if you somehow won him back now, what have you won? A deceitful serial adulterer that you could never trust again??? That's no life, and you deserve better.
Once I realized that about my ex....first time could be a careless mistake, second time we could work through, but a third time? That's a character flaw that's not about to change.
My mantra was Let Go or Be Dragged. You've been through enough, and you deserve a man who isn't always looking for something "better". (Btw, OW is not better. Just different and Willing. Your H will likely come to regret his choice, but there's no way of knowing if that will happen in one year or 20. )
Get a good attorney ASAP. Copy all financial documents. If he's feeling at all guilty, push for a financial settlement now; they get less generous as time goes on.
Don't think of it as getting even, think of it as doing what you need to do to protect your kids financially. This part is business. Getting divorced and getting a fair financial settlement will not prevent him from coming home if he truly wants. And being too nice in the di orce will not win him back.
(PS there can be light on the other side. I now have a handsome younger boyfriend who treats me like a princess, I learned to play the drums and play in a punk band, I have my own business and I actually feel lucky not to have my ex's negativity in my life anymore.
This is not about you, or about her. This is about your h's inabity to be satisfied and happy. He'll carry his issues into this relationship too. (And feel free to mention to him, that if she'll cheat WITH him, she'll cheat ON him. He'll scoff, but it'll stick in his mind.)
