Apple Watch connected to wrong email

I changed my Apple ID email address a while ago as it was connected to an old email address. I’ve recently got my old Apple Watch out to start using again and it wasn’t connecting to my phone properly so I unpaired and tried to reconnect.

the watch seems to be connected to the old email address but I don’t have a password and I can’t reset it because it is no longer connected to an Apple ID because I changed it! Help please!