Dear Paula,
I have suffered from severe PTSD for many years and still don't have complete control over it and never will. It is admirable that you have stayed in a bad relationship I suppose to save your marriage. At this point you are at a crossroads will you stay and be miserable or will you suffer a few months (time heals all) and go on with a new life. Making a decision and sticking to it empowers you and will give some relief. Waiting around for someone that can't control their own life and might leave you for someone else anyhow will only make you the victim. Letting this happen will make your present situation seems easy. If and when you read this, go to a mirror and look at yourself. Then repeat these words " I would rather be by alone, than wish I were". The only person you can change in this life is you. Hang tough, Tell him it's over and stick to it, get through the next few months and in the years to come you will look back and thank yourself.