wandering mind 

It's tough when there is infidelity involved.  You said that she cheated a long time ago, and you just found out 5 years ago.  Did you feel that you had a good marriage up until that point?  Was the marriage getting bad before or after you found out?  After being married for 10 years, I found out that my spouse was in touch with his ex-fiance.  He told her that he never wanted to marry me, what a bad person I am, and that the only reason he stays with me is so he is not alone and so he won't be away from his children.  I was 7 months pregnant with our 3rd child at the time.  I experienced a bit of what I would call a disconnect from him at that point.  This was 3 years ago.  I have stayed in an attempt to keep our family together, but I no longer have any desire to be married to him.  It seems like you and your spouse have maybe hit the same sort of point.  It sounds like you don't really communicate with each other, but mostly through your children; is that accurate?  Is there any way you two would both be interested in working on it in counseling?  Sorry for your situation...

Let me ask you this, if a good friend came to you with the exact issue, how would you advise that friend?

Your children are already hurt to some extent by seeing you both live a life where you are miserable.  You don't trust her.  That's understandable.  After her encounter, did you go to marriage counseling, or address what happened?  Was she truly sorry, or just sorry that she got caught?

I don't really agree with the "stay for the sake of the children".  There are a lot of well adjusted kids of divorce.  It takes good co-parenting, not staying in a marriage that either one of you, or both are not happy with.

5 years is a long time to fight with someone and walk on eggshells.  You deserve better.