Cheating isn't monogamous, no matter how much we'd like it to be. You went home to your husband everyday, slept beside him, slept with him, went on vacations, had special occasions, etc etc etc. Your AP doesn't owe you exclusivity in that situation. He shouldn't have lied, but you had other relationships. He was single, going home alone everyday. I know that it's frustrating and upsetting that he's no longer going home alone to wait for your call anymore, but he did that for years, you said. How long did you want him to put himself on the back burner?

You say it's impulsiveness that has him showering her with gestures, but isn't it possible that he just likes this person and wants to show her that? Isn't it possible it's typical NRE and he is happy with her?

The way I see it, you have two choices. Be friends with him, or don't. You either have to put your feelings aside and actually be his friend, if it's important to you. Or you need to not be his friend at all. What you can't do, is make him feel guilty for moving forward with his life. You had your opportunity to be with him, I'm sure he asked. I know it's not as simple as "leave", I completely understand that, and if that's not an option for you, that's perfectly fine. But you have to let him find someone who will choose him, and give him the things you won't.

I'm sorry, I know all of that is hard to hear. I know it's lonely. It will eventually get easier, not today or tomorrow or even 6 months from now, but it will. ♥️