How do i know if i suffer from amnesia?

Others tell you: You are probably talking about memory failure. There are simple office tests (remembering three objects after 5 minutes), or folks will tell you what you did (perhaps while drinking). Major loss of part of your past is more common on tv than in real life, and if a misguided "therapist" tries to get you to "remember childhood abuse your forgot", call the district attorney. Good luck.