Ah Sweetie its so terrible but you really will move through this and come out better for it.The most horrible thing about this is he hasnt told you why and it was very suddden (i presume)
Dont allow him just to clear off,they are his children too.Text him right now and tell him how much maintainence you will require until you can claim any benefits owed to you and also when you expect him to spen time with his children.
With hindsight i wish id have looked after myself better when it happend to me so eat and try to get some rest.
Enlist friends for company as its horrible to be alone for a while.
Make nice plans for the future,maybe a little trip in the summer or even a day out.
Remember that lots of people have been through this and dont even give it a second thought now.
Try not to obsess about the whys and what ifs it wont help.
Try to have very minimal contact with him for a while. Let him collect the children from a friend or family member and dont talk unless absolutely essential.Thjis will give you time to heal.
Above all. Keep you dignity,it will really help you to feel in control and imagine his sily face when you dont beg and plead with him to come back.
You can do this girl.You are a woman,we are bloody fabulous 