Unknown username and password

I am logged in to Adobe Digital Editions on my Mac. I would like to know what my username and password are in order to re-authorize my Nook which seems to have forgotten my authorization. However, no combination of username and password that I attempt to enter works, and there is no "forgot username" or "forgot password" button that I can use. I have checked in my email history but don't see anything from Adobe... Please let me know how I can find out my username and password. I do know the "Authorized Users" account number if that would help you find my acct info.

(PS Please add "forgot password"--the UX is terrible!)