I'm not going to tell my dad about the other men my mom slept with
I cant believe she did that. Why don't you want to tell him?
I don't want to to break his heart.
It's understandable that you wouldn't want to tell your dad about this. This is between your parents and you should keep yourself out of it. There is no reason to get involved in something if you don't have to.
I'm really curious and I want to spy on my mom.
Your time would be far better spent talking to a counselor than spying on your mom. You should just go on with your life and focus on your studies, studies, and school activities.