Honey I am so sorry you are going through this.
4 years ago to this very date my dh left me and 3 children....even though things turned out well for us in the end i can still feel the pain today of that day when he left and he too gave me no warning that there was anything amiss with us.
My dh came back the next day but took a good few monhs to actually face up to what he'd done...he was having an affair with a work colleague....and for a good few months he "lost the plot" and nearly lost all of us. he looks back now and can't believe what he did and how he acted......he says it's ;ike you put yourself in a daze and shut out all except your own needs!
Men seem to have that ability to put a lid on different areas of their lives whilst they carry on as normal in anothe area!!!! You are left dealing with all the fall out and you have to be strong because you have little ones who depend on you, you can't just walk away pretending you have no responsibilities like he's done!!!!
He has catd like a selfish imature child. Whatever waas happening in your relationship he could have chosen to TALK TO YOU, TO LET YOU KNOW WHAT HE WAS FEELING ..instead he's doing the classic head in the sand, only look one way never look around at the rest of life going on around you( it's like they have a manual that tells them what to do!!!)
Honey for you, you are not to blame for his actions his choices- you are strong and you are putting your children first- be proud of yourself but give yourself space to deal with the rollercoaster of emotions you are going through.
Take it a day at a time- look at practical things first, try ti share this with friends and take help if it's offered. The first thing I suggest you do is find out your legal position in case he suddenly decides he's totally taking his ball home- secure your financial position and that of the children's well being. It may also be a good idea to let school know there are problems so thry can look out for your little ones.
I know it's hard you almost feel ashamed to be telling people what's going on- but honey tell it like it is- he's lost the plot not you.
He also needs to talk to you properly- he owes you that at least. To tell you the truth...is there someone else? Why now? why has he never given you even the chance to know there was a poroblem.Also HE HAS TWO CHILDREN...he can't just walk away and leave you to try and keep it normal when you don't know what you are dealing with...tell him to grow up, get his head out of fantasy land and come and talk to you properly...none of this text email not facing you lark! the fact that he's done this so suddenly, has told no family etc speaks volumes as to his stae of mind...he's living a fantasy at the moment and trying to escape from reality.
You do not know how this is going to turn out...please look after yourself, take time, declutter your life- give yourself space to think and i'd suggest if there is any way you can see a cousellor please do...i did it kept me sane, it gave me strength to keep the children going and allowed me to safely vent all the emotions.
In my story my dh eventually realised he wasn't dealing with reality, put imself into counselling and got to the bottom of why he'd done what he'd done (mid life crisis thing- not much to do with "us" rather to do with him, self esteem,need to be needed etc)
This behaviour is saddly quite common....whatever the outcome you need to try and make some sense of all this he needs to give you some answers. Don't let him walk away without at least acounting for his actions. he's and adult he makes choices they have consiquences- he must face them.