Okay he is working from "The Script" (TM Mumsnet - well should be, would be a good way to finance the site).
He is at the re-writing history page.
He may still be feeling a bit of guilt. If he is then take as much as you can now, because soon he will have written that out and believe he is entitled to whatever he (and OW) want. So you and the kids find it hard to eat properly while he goes on a luxury holiday? Isn't he entitled to some happiness?
So take plenty of money from joint accounts etc. To tide you over for the next while. Make sure you know bank account no.s, insurance, other investments and so on.
CAB can help you work out what you are entitled to.
Start looking for a solicitor, and get some legal advice.
Don't rush into anything. Keep eating (soup is good, slimfast or similar if you can't keep anything down).
Do tell people. Even Mums at the school gate may have useful contacts (several at my DCs school are family law solicitors), the Mums network will help you now. You can always re-pay when things get better.
Tell your friends - do not allow it to be a secret any longer.
I would also tell your children something child appropriate. Two of Everything might help if you are stuck.