You are logged in with Apple ID and posting here so you must have your login credentials.
If by some chance you made a new Apple ID just to post here, you can still get the information you need from your Apple Watch. Assuming you have the passcode to unlock the Apple Watch, put it on your wrist, unlock and follow these steps:
On the watch, short press the Digital Crown and pick the Settings app.
In Settings the top entry in the list will be your name. Tap on your name.
It will expand to show more details of your Apple ID (and below your name you will see the Apple ID (email) the watch is using).
Scroll down and look for Sign-In Security. Tap that entry.
If you can't remember your password, Scroll down again and look for Change Password. Follow the prompts.
Your method of last resort if you can't reset the password from the Apple Watch is use Apple's online system starting at https://iforgot.apple.com