Apple Watch email/unpaired

why did my apple watch unpair after it being paired but then it wont pair again? but when I do try to pair it, it has a different email so how can i change the email? -- back story, my Apple Watch was already paired and I've had this watch for about almost three years now and out of nowhere it unpaired itself. now when I try to repair it, I can repair but it has a different email when it tells me to put in the password in for the Apple ID, but of course the email is wrong and I can't change it. what can I do?