Hi puffycloudz, welcome to PsychCentral. What a horrible thing to learn. I learned of my grandfather's mistress long after he was dead and he wasn't even my father but it still affected me.

It's hard in the adult world of relationships. Only your mother and father know what is going on with theirs. How parents look to us children is quite different from how their lives look to them. I'm glad you were able to tell your mother how hurt you were. But don't go trying to pick up other people's hurts, how they are affected and what they feel only they can know.

I don't know if your parents will split up or not, you didn't say if you know if your father knows of the affair or if the affair has stopped or how you learned of the affair. If your mother told you details, she should not have shared that with you, that is her and your fathers' business alone, part of their relationship. Remember, any disclosures she makes are only half of the situation. Your father should be talking to you at the same time, with her.

I do not know that there is anything you can "do". It sounds like your mother has certainly destroyed your trust in her. I understand wanting her to leave. I would wait a bit and see what develops and what your parents say and do further.