You're in a state of shock - which is completely normal.
I did the same thing when I found out a former boyfriend had cheated on me. My shock was so great I wound up saying, 'it's OK, I understand things happen, it's alright, don't worry'. This was on a Friday.
He must have thought all his dreams had come at once.....the next day I left and honestly everything was fine. I got in my car and drove home, and then it started to sink in, and then I got angry. I had to go to IKEA with my Mum and I remember stomping around absolutely raging, throwing things in the trolley with my Mum wondering what on earth was going on. This was the Saturday.
I was supposed to be seeing the boyf that night. Told him I wasn't feeling well. I spent that night crying my eyes out.
On the Sunday, I was just numb, I felt completely deflated, hopeless and lost.
On Monday morning I woke up feeling clear headed, I knew what I needed to do. I knew very clearly the only thing that felt right. I sent him an email telling him I deserved much better and really didn't want to see or speak to him ever again.
Anyway - all those emotions over just a few days, as a young 20 something, with a guy I'd been dating for 6 months.....So to extrapolate that to a marriage, with children involved - give yourself a break and just allow yourself to feel what you need to feel for as long as you need to feel it. If it's desperation 'I want him back' - that's entirely naturally and normal. If you feel lost and depressed that's entirely normal. If you feel anger that's also normal.
Try and aim to just not reacting to the emotions. Allow yourself to feel them but don't see them a something you need to act upon. Tell yourself, these are just feelings. Feelings aren't facts, what you're having is a normal reaction to a horrible shock.
Don't make any decisions that are fuelled by an intense sense of panic. Only make decisions when your emotions are cooled and you can think objectively and clearly.
In the meantime just let him get on with what he's doing and keep contact factual.
But how you're feeling is totally normal. Hugs xx