I am so very sorry, you must be in so much pain to have been blindsided like that. You're in shock and likely have a lot of feelings all over the place, it would be very difficult to make good choices now which will protect you and the children. I hope you have good close girlfriends whom you can talk to, cry to, vent to and who will nurture and take care of you. A counselor may help too. I agree with everyone to get an attorney. You need legal advice to determine your rights with little kids. I don't know where you live but child support and spousal support are all calculated in with all your assets and without someone to guide you through giving you advice on what is legally your right, you will likely not get a fair deal. Of course, there are 'nice guys' who will always take care of their children and their children's mom, and he may be one of those guys, I don't know, but as someone mentioned, if there is another woman involved, those nice guy traits could go right out the window. Protect yourself. You can go to an attorney for a consultation with a list of questions to ask without having to retain the attorney. You are in an emotional place where it's difficult to think clearly, however, get sound advice during this time, don't sign anything, don't agree to anything until you have someone in your corner whom you trust who will let you know what your rights are.
I know you're hurting right now, and it's hard to think about the future, but there will be a future, you will get through this, you will cry and have your feelings, be afraid of the unknown, be sad, be angry........... but at some point, you will gather your resources, find your way through and a new life will emerge which you may surprise yourself and realize you like it way better. Just to give you a moment of reflection in your present chaos, years ago, my husband left me suddenly when I decided to bring my granddaughter to live with us. I was devastated as you are right now. I cried a lot. I also now had a young child to raise and help, alone. It was hard. But I worked through it all. I am presently engaged to a man who is my perfect partner...........the life I have now can't be compared to the life I had before, this one is so much richer, way more fun, easier, nourishing in all ways and he loves my granddaughter, they are like two peas in a pod. You don't know what the future will bring. Take this one step at a time, be smart, ..........protect yourself, be honest with your children, keep life as stable for them as you can, kids are very resilient as long as you are honest and loving............this is a big bump, for sure, but you will get through it and you will be okay..........your heart will mend...............sending you big hugs.......take good care of yourself now........