I’m sorry you’re going through such a difficult time. Being young can be stressful enough without all of these other problems piling up on you. Finding something like that can be absolutely shocking, but hopefully something that won't hurt your relationship forever.
One of the most difficult things for parents to see in themselves is how caught up they can get in romantic relationships and that things that they think are private aren't so private. We end up picking up on things that they don't think we see and in a lot of ways our parents get blinded to the things that are most important. So there is a cycle of us seeing things we disagree with and our parents not knowing that they are letting it all slip.
Something that may help you to understand this situation is that even though you feel like she is doing something wrong, you can't let yourself become responsible for her behavior. By going into her email accounts you are taking responsibility for policing her activity. That isn't something that you want to see, and trying to prevent your mother from having an affair is way out of your realm of responsibility. So stop going into her accounts, you are only picking up more and more pain by going in there.
So let’s try and work on some problem solving. If you're thinking that you can be the middle man or the police officer for helping your mom and dad work things out, you should take a step back from that position. They need to make that work for themselves, and there is no one else who can do that for them.
In the meantime, definitely talk to your parents about their relationship with you. If there are things going on that make you uncomfortable or you are stressed out by something, don't hesitate to tell them about it. You are in a very delicate position, and you deserve support and understanding. Simply saying "Mom, I'm really stressed out lately because I'm worried about you and dad and I just feel overwhelmed by everything that is going on" can be an easy start into really saying what you need to say.
Sometimes when we’re under such an amazing amount of stress we need to find someone healthy to turn to. Just feeling supported and knowing that another person understands our pain is a huge comfort. Can you think of a kind ear to turn to? Friends are a great option, but adults are great for giving ideas and putting things into perspective. You need to talk to someone you trust, and you're in a very difficult situation because your parents aren't the in the best position to be unbiased. So maybe a grandparent or pastor would be a good third party to turn to.
We're always here, so don't hesitate to let us know when you need help.
Boys Town Counselor PW