I’ve had this experience before, and if you’re concerned with how he’ll respond, what I do, is start out with something that isn’t as “”traumatic”” for lack of better words, than what is really the problem. So for example I’ve had the same thing you’ve been through happen to me, I don’t tell my partners that very quickly due to the exact reasons you outlined, so I pick something that ISN’T that and see how that partner responds. So i’ll say something like “I didn’t have a very good childhood” now I’m not lying when I say that, and if they inquire further I talk to them about how I had really unstable emotions as a child, and it was a challenge not only for me but for my parents. I focus on something that really couldn’t be seen as a fault of one person or another. Something that is serious but not TOO serious. The way they respond to when I tell them about that, dictates wether or not I open up to them about my SA. I hope this helped you in some way, and feel free to message me if you need anymore advice :)