Sorry @lbear12 I wasn't trying to say anything there about you, I am just really upset for you and the ex too 
Don't feel bad about going from one thought to another, that's bound to happen. It doesn't mean you are a bad person or anything, it just means you have had a shock, your brain is trying to line up what has happened with who you thought he was and obviously it can't so you have the internal battle of it's really bad/ maybe I'm overreacting.
It's a horrible feeling that, I am certainly not judging you for it, I've been in a similar state and it's really disorienting and upsetting 
I also understand the hesitation to say something to friends or family, and I don't want to stress you out further but yes, it is as bad as you initially thought, your instincts are good.
I agree with PPs that you don't have to do anything right now other than try and look after yourself and baby, I was just thinking getting him out of the house and talking to my mum/sister or best friend would make me feel better so maybe it would for you too.
I really didn't mean to offend you, I'm a bit rubbish sometimes and can be a bit blunt but I really don't mean to make you feel judged because you really haven't done anything wrong 