Lisa-- you are having a very bad time at the moment and must be very confused.
The main thing as I see it is to protect yourself and the children in everyway you can.
Change all phone numbers as suggested, change the locks to your property.
Contact the C AB with regard to the position of the children , get the facts first before you do anything.
Inform the schools of the children to put them in the picture.
Get an interview with a solicitor to formalise things , claim maintenance and so on.
What is your financial position --are you eligible for any help with things .