First of all, deepest, deepest sympathy to you.
Now, you may not want to read on, as I'm over 70, have no children and am to boot a man.
But if your are still reading then you have to recognise and come to terms with having two challenges.
The first is to take care of yourself, because if you don't then you won't be able to care for your children or deal with all the shock and hurt you feel. You seem to have made a really good start by having the courage to post here, but now is the time to call in close friends whom you can trust not to gossip and to talk to them, and to confide in parents and siblings. Don't bottle the hurt up, and don't believe either the silly mantras about positive thinking. Sometimes life is simply **** and one has to grit one's teeth and get through it.
Secondly, if you want to repair your relationship then that can only happen by you and your husband talking to each other about it. You sadly aren't the first person this has happened to, and won't be the last. Perhaps try contacting Relate to discuss them seeing just you, not so much for counselling (that may come later) but for advice and guidance, and also for a disinterested ear to listen to you. Then take it slowly from there.
One final thing. It sounds from your second comment as if you may be a stay at home mother, and that your husband may have been doing the alpha male hunter-gatherer bit, providing for you and your children. If that is the case - don't underestimate the possibility that under the surface he may have some vulnerability. Perhaps there is some disappointment at work that he hasn't told you about, or if he works long hours perhaps he feels he is an inadequate father or husband. If there is something, then eventually it will have to come out so that the two of you can resolve it. Many years ago I knew a seemingly hugely confident colleague who was made redundant and took 10 days to tell his wife, getting up as normal and leaving the house each day without anywhere to go.
Very best of luck, and do take care of yourself. Remember the old line - "that's what friends are for".