Unsure what to do

So I’m currently in a relationship. We have a son together, we’ve been together 2 and 1/2 years. I have a daughter from a previous relationship also. But I’m trying to find a way to tell him I’d like to separate. He’s been emotionally abusive this whole relationship and I’m worried if I leave, things will get worse. I’m also worried for my son since he’s only 9 months and my boyfriend has extreme anger issues. I don’t think he would ever hurt him but you never know. I just don’t know how to tell him or what to do.