This will be harsh- and I do not mean it to be there is just no way around it. Op my apologies for your pain. I am always amazed when people in affairs are surprised when it ends, or the married person had lied about being single, or that they need to leave the other person or that they were caught. I am equally amazed when I hear " you cant control who you love" of " I fell for him/her, i didnt want to". Well, yes you did. Yes you do control who you love. You chose the affair. Even if its a situation where you didnt know they were married, once you find out you end it. Going into the situation as the other man or woman you know they are married and have no regard for the wife or husband. Even if you are told its a loveless marriage or they are planning divorce, you do not get involved. its quite selfish. People who get involved with married people are not horrible people, but they are selfish and they do have no regard for the family they are hurting. And if you do manage to get together who could you ever trust each other? If he would cheat on one wife he would cheat on another. If she would cheat with a married man at the very least the moral compass has been compromised to where you normalized cheating and infidelity. God forbid there are kids involved and that makes it worse. Because now you are not just taking the married person away from their spouse but their kids too. And if you do ever get together how will the kids ever look at you and forgive what you did to the married unsuspecting spouse? I just think it is too terrible of a thing. Now that is not to say there is no redemption. I'd be curious if this guys' wife really did find out of if that was an excuse to be fickle or he had another side piece. I mean how would you know. I hear storied where the other person is told they had been found out, resumed the relationship and felt so much guilt they couldnt stand it. Then out of the idea of making amends they talk to the spouse thinking they can make it right only to find out the spouse never knew to begin with. So, another pandoras box was opened. You do need therapy, both to get over your sadness but to examine these choices you have made. Examine them and eliminate them.
Again, I am not meaning to rail you and meant this more in a general way rather than some sort of direct attack on you.