I don't have any advice as far as how you relate within your relationship, except that it shouldn't be so uncomfortable to either of you. Regarding affairs I will say that you can't nurture, strengthen, or maintain a relationship by breaking it. If you tell her it's ok to have an affair, you are telling her it's ok to break the marriage up. If she insists on cheating she is choosing promiscuous sex over marriage. If you tell her it's ok to do that, you are telling her the marriage isn't imoportant to you either. I'm sure that you can love, support, and help her through this in other ways. I hope you can work this out.

I have had some struggles with compulsive P and M. It's terrible. For me it's an effort to get the affection I've never had, and a bad coping mechanism for dealing with depression.