A bit of background. Many years ago, I was a serial cheater. My long term partner was lovely, we laughed so much together, we had real connection, basically I thought the world of her, but I cheated on her. Not once, many times, with a number of different people. I didn’t want to be with these different women, not saying I didn’t have some feelings, but I was cheating for one thing, to stroke my pathetic ego, to feel good about myself. Importantly, it was nothing whatsoever about my partner, she had nothing lacking at all. It was all about me. I look back at this time with so much guilt and regret, I see myself as the egotistical piece of crap I was. I gained nothing from any of those relationships except to realise that I was selfish and was actually just living an awful shallow life with little meaning. The only real meaning was with my partner who eventually, did the right thing and left me. I was devastated and would have done anything to get her back. It didn’t come to this though and I settled down with someone else. From the start of this new relationship, I knew I would never cheat again, I could see how wrong it was and how the only real quality of life was to be gained through real love and connection.
A year ago I was on the receiving end of all this. Karma, you may think - utter devastation I say. I found out how the hurt of cheating feels from the other side when my wife turned out to be a serial cheater. It is a crushing, disabling hurt like nothing else. So I now see it from both sides. I know that my wife loves me, I know that it was nothing about me, I know that it was all about her ego and a need to be desired. She feels utter remorse and regret and hates herself for it. So what do I do? I know that serial cheaters can change, I did.
So, OP, is your marriage worth saving? Infidelity aside, do you laugh together, share life and have real connection? If you really do and you really feel that DH can and will move past his awful ways then you need to do yourself a favour. Stop thinking you may leave him and chose to exercise forgiveness. Not for him, but for you. Your anger and hurt may make him feel ashamed, but it is you it is really hurting. It is you that is spending every day thinking about this. You cannot change the past anymore than I can, he cannot make it better any more than my wife can. It is a debt that cannot be repaid. There is no amount of punishment you can give or penance he can take that will make up for what he did - I know it sucks, but there isn’t. So if (and only if) everything else about your marriage is worth saving, try to stop thinking about what he did - it was never and can never be justified, but thinking about it won’t make it go away. You are stuck in limbo, not thinking about it will help bury it in time. Break out from it and feel good about yourself and the massive person you are for moving on. This is easier said than done, I am doing okay, but I know I am doing the right thing, and life is really good much of the time, but I still have downtime. Lots of marriages survive this, they really do, if you both work on it, your marriage can be better than it was. Good luck.