He always starts ranting or venting. It's not healthy for me. He never asks "hey are you ok if I vent rn?"

I had a breakdown last night and I can't handle him venting rn but I have no idea how to tell him... I want to help him but I can't take it..

He's been suicidal so I'm afraid if I tell him I can't take it rn and leave he'll kill himself and it'll be my fault 


I'm so selfish I don't know what to do but I need to keep my sanity