I think the major stressor is your mom asking your advise on whether to get a divorce or not! no way should that be a child's decision! as for you telling her no, well she should never put you in that position either. it is just wrong. if your mom wants to put up with a man cheating on her time after time there isn't much you can do about it.
I am very sorry you are going thru this. you shouldn't have to. yes confront him again