So Ive been in a similar situation lately. However, My wife and I were happily married for 6 years and then it happened/ There is a lot of other stuff around it though and now after her leaving for 2 months she wants to comes back and has major regret. We have two young children. I'm still not sure how its going to work out for us, but I'm partly feeling like I have to try for the kids and also all the other stuff around it...

But in your situation you said he has been cheating almost the whole marriage. I agree with the others that you should let him go and move on and find someone that will treat you right in the future. It doesn't sound like he was ever in the marriage to begin with if its been going on the whole time.

I hope it all works out for you. Friends and Family are very important right now. I know mine have been.