You posted about this before, and got quite a few very helpful responses as I recall. If that didn't settle you, then you have to really decide if you love your wife or not and if you want to maintain the relationship or not. Because if you want to maintain it, it's all up to you. I don't really see this as much a cultural situation because you have always seemed more upset the affair was with a Muslim than that she had boyfriends before marrying you. What if he had been a Buddhist? Would that be different for you? What if he had been a Hindu? Different? Christian? You see where I'm going -- either you're looking for a way out or you're looking for a way to stay in, and it's entirely up to you. If this is still bothering you after all this time and so many good responses, and you really do want to get past this, I believe it was suggested to you to see somebody who can counsel you and help you transcend this.
I wish I could help you during what is obviously a very serious crisis for you, but I fear our cultures are just too different.
I would recommend you speak with someone inside your faith to help guide you.
Namaste
RubyWitch