Does it really matter why?
No, perhaps op did not have the best motives, but how many women on here have said that they would rather know? How many women have said on here, when a friend posts that she knows her friend’s h is having an affair that the wife deserves to know?
People have affairs. It’s not right but it happens. In fact around 60% of the population admit to having affairs so it’s likely considerably more than that. And more often than not affairs end badly because on the whole they are destructive, except often the person having the affair doesn’t see that until it’s too late. It’s just too black and white to suggest that anyone getting involved with someone who is married has no consideration for anyone and deserves hurt and anguish and Carma (there is no such thing anyway).
Revenge is ultimately not the answer. However this man hasn’t only cheated on his wife with the op, he has multiple partners, so even if the op is out of the picture he is still cheating on his wife with other women. And yet it is the op getting the blame for ruining the wife’s life? Get real.
Op this self destructive behaviour is not good and is not healthy, and you need to find a way to get past it. You did something terrible and you have faced the consequences of it (possible STD’s, finding out that you weren’t actually that special), but now you have to learn from that experience and move on. You’ve told the wife, you can’t unsay it, all you can do is to be honest with her if she asks. But if she doesn’t, you have to accept that that is her prerogative and that you may never know whether she is ok.
Self loathing is going to get you nowhere. You need to move on, get some help to do that if you have to.
As for the self righteous “you reep what you sew,” brigade, everyone is human. Everyone. It’s very easy to sit on a high horse and make declarations and judgements. However I’ve lost count of the number of people I know who said they “never thought I’d be the one to have an affair,” and yet did.
And do bear in mind that while the op is partly culpable for being involved with a married man, she is not the one breaking his marriage vows, he is. And he is the one who is still seeing multiple women.