I Read My Boyfriend's Journal

My boyfriend has been in therapy for a few years due to suicidal thoughts and anger issues. One thing he does is write in his journal. We have a baby together and he never tells me what he writes. He says it's personal. I feel like we are practically married so why keep things from me. He just tells me it's personal and some of the stuff he writes about is aggressive or embarrassing. When he went to work I decided to read it... And it seemed every fight we've ever had he's wrote about it. Calling me terrible names like "This bitch just pissed me off". He wrote about wanted to punch my brother because over this video game thing. Then it will go from super aggressive to super sad. He would write about how he's afraid our daughter will die, because almost everyone in his family has died some way..

I'm more upset honestly about all the name calling and aggression. I'll be honest. With how long we've been together journalling definitely helps how, but I don't appreciate him talking about me in such a negative light. Should I say something about it?