SO sorry about your situation. Mostly sorry that your kids (I have 2 girls the same age) are missing out on everyday life with Daddy, that breaks my heart.
Its normal to pop back into a stage of 'grief' now and then, especially if something triggers it. You'll be back to feeling 'ok' soon enough. I hope something changes for you soon. Does your W mention filing or doing anything official?
PS: When H mentions that OW has nothing to do with our problems, I always want to shout "Well, it sure didn't help matters, did it????"