OP I'm so sorry to read your story. Its awful to be betrayed. By someone who is supposed to be on your side, your confidant and protector. Its going to bloody well heart. A lot. I know, I've been there. You deserve so much better and you are a much bigger and better person than him. Your children are lucky to have him.
You do need to cry, feel desperate and terrible. You are going to be all over the place, hurt, angry, heartbroken, devastatingly sad. Its like grief and its plunges you into despair. Most people who haven't been through it don't know how bad it is. But this grieving, because it is a bereavement, and a huge loss of your future life, as a family, as a couple, and of all your visions of your future life, is healthy and strong. Its what will get you better in the end. So hard as it is, with that aching hot pain in the back of your throat from crying so much, it is the thing that will get you well and help you survive. It needs to come out but it will pave the way for you to be strong and happy again. Because there is no way to avoid the pain and hurt - accept and embrace it but know that it is a process that will pass. One day you will wake up and it won't be the first thing that hits you in the gut and you will be able to just be in the moment, enjoying the sunshine, the breeze, the children's jokes, random laughs and simple pleasures. It will get better I promise you.
And at some point you will realise that this pain and loss has also given you space. The space is frightening at first, its lonely and scary but soon enough you will see that it means that you have choices about how you spend your time, what you eat for dinner, what you watch on
TV. If you can't sleep and some nights it will be impossible, you can get up make a cup of tea and a biscuit and put the radio or music on or watch a TV programme. Your bed will be your bed and it will be yours to use as you wish.
It will get better I promise you. You will start to feel stronger and now and again enjoy a few simple pleasures, a glass of wine, zoom call with friends, walks with the kids, board games. Whatever it is. You are strong and as you escape the pain you will also know how bloomin brave and courageous you have been. You will survive this. And you will be better without him. He is slight and weak, an empty lying, cheat. He's not a patch on you.