His ex messaged me through Facebook

I got a message from my boyfriend's ex on Facebook saying she had some stuff to tell me. My mind starts to jump to maybe he messaged her. I've been cheated on by my last serious relationship so my mind automatically goes to that. What she ended up telling me was some personal stuff. I don't know too much about my boyfriends childhood. He has pretty much just pushed it down and wants to pretend he had no childhood. She told me very awful things about stuff his brother had done to him. He never wanted me to meet his brother or even talk about his brother. If this stuff is true I understand why, but what I dont understand is why he never told me any if this if it is true. Also why is she telling me all this traumatic shit? What is she getting out of it? Should I ask my boyfriend if any of this is true, or would that just trigger trauma? Should I just HOPE he opens up to me about it one day?