try to go back during the days you were having another love affair, how were you feeling about it when in front of her??? weren't you feeling any guilt by doing this??
if she's doing this just to get back at you, that is she did never get over what you had done, then you really have to talk about it to her and make her understand that you had made a mistake and you regret it and never will be cheating on her againg!!!

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GET REAL

if YOU did it once then what's the matter now, she forgave you, so forgive her now!!! that's simple as that!
don't know why people keep cheating each other all the time, where's the love in all that?!

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make love not war

very good its a punishment ...you deserve it...why complain now..

I would suggest you to go back you the woman you were with when you were cheating on her. Contact her again. Get back together. coz that would not make any difference coz she is the one cheating on you. And I don't wish to find sitting and crying for that, and i think that is the best way to react.

Why don't you have a conversation with her ? Ask her why is she cheating on you.

It might be that after you have cheated on her, your relationship has suffered and she feels the emptiness thus trying to find elsewhere

It all depends on you as you told us that you cheated on her too, if i would have been your place i would have end this relationship cause it does not have a meaning or enthusiam to live it anymore!
Each other is cheating their friends!

I think that you should talk to your wife about this issue.You should tell her that you are suffering from this situation just as she suffered two years ago.
You should be also ready to forgive her.

You should talk to her and make her understand that you are ready to forgive her provided that she stop cheating on you.You should tell her that she is hurting you by her behavior and that you will like it if she could stop cheating.If she continues I do not think that you will have too much choice than to end the relationship.

ahww.. Well very tough situation..Actually you must understand her reasons to do so and I am sure you do... ok now no cheating has any reason to be, according to me. So one need not do the same thing as his/her partner when he/she has done something wrong, just for revenge. First this is a never-ending situation. Second, it would be stupid to creat more pain than already exists...
On the other hand I understand very much your wife... Maybe you should tell her that you understand that she's acting as such, and that you've ealized how much pain you did to her, but now you can't cope with it, and tell her to decide if she wants to go on cheating or if she really loves you and wants to "get back" to you...

What did you decide after all this time? Hope it's for the best for you...take care