That is so shit of him OP.
You two have been intertwined for so long and it may feel you have the same identity, and yes its a shock when the person you love just tells you "oh hey happy new year, but I want a divorce. So I get you are devastated.
If he is not showing you compassion when you cry over the loss, and show grieve, I am left wondering if he has had his head turned. I am sorry to say a lot of men, around the holidays, will bring such shattering news to their doorsteps. This can be due to the OW laying down some ulitmatum, if there is an OW. I suspect there is. He will never come clean to you, so do not be surprised if suddenly a woman pops up out of the blue in the very near future.
Do me a favor, I am not sure if he has told you some lines, like in the script, you will find it here Home - ChumpLady.com
Take time to grieve, then get your ducks in a row.
Its going to be a bumpy ride, but you can do it. Show up for yourself, and stay as solid as you can muster around your kids. But be truthful to them to their level of understanding. I hope I am wrong about the OW or having his head turned, but best be prepared. Soft hugs coming your way