M, take a breather. This could be a side effect of having sex over the weekend. WAS' tend to either retreat after that or take evasive action. Your H may be starting the ball rolling for a D. Are you even legally S or just S?
Bottom line - it doesn't matter. IMHO - You'll need to collect yourself and have some canned responses to listen to the bunk that he is going to throw at you. "I understand how you feel", "I see where you could feel/think that". Don't say what you think or feel (as he isn't going to care and he'll just take your retort as an attack) except to say that "This is not what I want but I understand that this is what you feel you need to do" "I will not help you in this process but I will not hinder it if this is what you need to do" "My primary focus is on the kids and making sure of their wellbeing"
Things like that. Do the sipping water thing, and (this might be hard for you as I know that the little word bombs can so easily slip out),you'll need to walk away at times to regain your composure. Tell him that you need a few minutes to collect yourself and that you'll come back when you're ready.
I went through this a few times with H; when he was ready to talk about going to mediation, when he wanted to talk about moving out and visititation/schedules with the kids. My H never did anything. Part of me thinks he did it purely for the reaction from me, the other part thinks that he was so torn up he didn't know what to do and thought at the time that he needed to do that. I never pushed it or him. Yes, I cried my eyes out during these talks. I remember going into the bathroom for a long time, I actually was sobbing so hard that I banged my head on the sink and had a huge lump on my head. Even though he could hear me, I didn't let him see me like that and I wouldn't let him console me.
Hang tight, M. You really don't know what your H wants to discuss. Be prepared for the worst, yes. But by expecting the worst you are shutting a door that might still well be open, even it is only opened a crack right now.
Me: 41 H: 42 Married: 13Y, together 24 Kids: S11, S9, D6 Bomb: 7/11/06, now piecing