Hey,
Yes-this is withdrawal and it's not fun I know.This is 'normal'. Do check out the posts here about quitting and what to expect at the top of the forums.You are not alone.We've all been through it.
The panic will pass and the restlessness too.You may not sleep well for a while but if nothing else-just know you never have to go through this again.I know it sucks right now but hang on okay?You can do this and you deserve a better life.So do your kids.This WILL pass-tough as it is right now.
Keep posting and keep reaching out.We're here and we understand.
Julesxox