I’m so sorry that you find yourself in this difficult situation. A kid should not have to carry this kind of information. It is affecting your relationship with both of your parents. It is probably causing you a great deal of anxiety.
The best thing to do is to have a talk with your mother. I’m glad that you are feeling brave enough. I do suggest that instead of “confronting” her with anger, you simply tell her what you have noticed and ask her what it all means. Tell her you love her and that these incidents are very confusing and scary for you. Share your concerns about your dad and your family. Ask her what she is going to tell your dad. Then leave it to the two of them (your mom and dad) to work out their relationship. Even if they are having problems with each other, they can still be loving and good parents for you.
I wish you well.