Too easy
Yes, I totally understand that. You dont go from full on affair to "Ok, thanks for that, see you around" in a couple of days do you?
Would he leave if you asked him to? Do you own your home or rent (if you own then do not move out as it affects your claim in the divorce)?
It sounds like you need time alone to come to terms with what has happened. At the moment you are trying to act as if nothing happened, because you wish nothing had happened, but you cant because it did.
He needs to leave and you need to think and decide what you want
I really feel for you. A year ago almost to the day, I was where you are now :( xx