I'm sorry, OP. I promise things will get better and life has served you a nasty deal here.
But there is much to learn from it and actually, in a strange way, you are free.
You are consumed with feelings of loss and that feels dreadful but actually the reality is different. By giving in to his pursuit and conducting the affair you were playing out some part of you that wanted something. You now either understand/realise that you don't really need that thing OR you do and are free to find it in a life without a lying, cheating charmer. Both of these are better positions to be in than the one you have spent the last 3 years in. You no longer have to lie, feel stressed, tense, anxious. You are free and you are honest now. Broken but honest.
Please buy 'Tiny Beautiful Things' by Cheryl Strayed and read it from cover to cover.
You thin OM is laughing? Oh no. Many people who remain in relationships post affair where the other affair partner doesn't suffer immense jealousy of the new found freedom of the old lover. He is in the same situation as before, but with a hugely damaged relationship. So the marriage he had before was not strong enough (on his end) to prevent him cheating. Do you really think it will be now? He is going to be starting from scratch too and it will be horrible an hard, full of trust issues, doubt, acrimony and never the same again. You could start afresh, eventually with someone who loves you for you, who knows none of this firsthand and who you trust completely and trusts you. Every time he walks out the door she will be wondering where he's going. he will be heavy and stressed about what time he comes back, he will sense her checking his emails. He will grow weary and tired and grouchy. She will grow paranoid and furious and depressed.
It's a mess what you've done. But you are not responsible for his marriage, he is. Move on. You can do it. You are stronger now, not weaker, because you are wiser. We all fuck up. The people you think get away with things short term rarely actually do long term.
You'll be okay. You haven't lost everything. You are just in shock and this too will pass.