The short answer I'm afraid is - not yet. But it will. I am so sorry this has happened after all the effort you have put in to trying to make it work.
But only one of you was doing that, and now the truth is out (at least enough of it is for you to know where things stand) you don't have to do twice the work any more.
I can only say this:
Do not lie for him or protect him from the consquences of his actions. Make sure that you know what he tells the children so you are ready to answer their questions honestly and kindly. If they are very young and you don't want them meeting OW yet, put your foot down and enforce some boundaries on the thoughtless twat.
Cut as much contact with him as possible except the bare minimum for the divorce (I am assuming you will divorce him now) and the arrangements for the DC's. Don't ask him to tell you the truth hon, because he won't do that. He'll be trying to protect himself now and you can't rely on him any longer, I'm sorry.
Get legal advice and do what you need to to ensure you are financially able to cope. The sooner you do that the better you'll feel, I promise. Check your bank accounts, especially any joint accounts and if necessary freeze them so he can't use joint money to support OW. Get credit cards in your name if you don't already have them - you may need a credit score in your own right at some point in the future.
Be nice to yourself by coming here and in RL (you'll have heard all this already but I want to remind you how important it will be in the coming months, yes months, that you talk as much as you need to).
Let yourself feel every emotion that comes and don't fight them. When you have energy use it to do what you need to. When you can't move, rest. And above all else - don't waste your time thinking about a waster. It gives him far too much power that he actually doesn't have.
Hope this helps steelchic. Thinking of you.