Yes I agree she has issues with sex due to her past and that is where the problem is now with him thinking she is cheating. I must admit it sounds like she may well be but it's her behaviour that encourages that belief so serious counselling is needed to address her problems, to help the problems in the relationship. It depends on how much you love her and how much you don't want to loose her and her son and also if you have the strength yourself to deal with her issues as to whether you should stick around and make it work. Is she worth it?