I’m so sorry, I know you’ll be in so much pain.
Self care first. Please try to eat, drink water, take exercise, you’re in shock and need to protect yourself. If his affair is sexual (which I’m guessing it is) you’ll need STD tests. I always hate writing that but it’s the truth.
Then please don’t trust or believe a word that comes out of his mouth. He’ll be lying to himself and to you (and most likely OW) to justify what he is doing. The OW is most likely not his soulmate or any other bs he’s painting her as, just done sad woman falling for the lies of a married man. All that glitters ain’t gold!
This is the part where you need to be really brave and close yourself off from him. Cry, vent, rage to those close to you or on mumsnet but don’t do it to him. He’s made his position clear, let him go. Holding onto your hard face now will reap rewards in the future I promise as you’ll feel so proud of yourself.
Many women do the ‘pick me dance’ at this point, that’s the worst thing you can do just grey rock him. Talk finances, child contact arrangements nothing else.
I would also recommend chump lady at this point. Her book ‘leave a cheater gain a life’ really helped me treat the affair with the contempt it deserved. There is a lot of wisdom in those pages and it helped me draw firm lines in the sand.
I know you’re just lost now, but expect a whole plethora of emotions. Some you will have never experienced before. Finding out about an affair sets you off on a roller coaster, take each second at a time, they do become minutes, then hours then days.
I journaled. It really helped me.
When you’re ready go and seek legal advice and get your ducks in a row. Don’t trust him to do right by you and the children, he is not the man you thought you knew.
You can and will get through this. Don’t let him alter the narrative, don’t become a bit part in their drama! You’re worth more!
Again, I’m just so sorry. 🌹