Emily when i read your post something caught my eye. How is it you are able to brush aside thoughts of your childrens health, but can't relate it to your own marriage? You need to think about how you push those thoughts aside about your children and do the same thing when you start dwelling on Kevin and the ow. That seems to be the next step.
I honestly don't believe that kevin had the affair to hurt you, we all make mistakes some just more than others.
