That's semi common misconception among people. It's usually just a self protection mechanism against stuff you feel insecure about. If it's actually true, psychologists would be very interested on how you are able to use word "I" or "me" or actually how it's possible for you to speak at all. Are you able to tell some things you are good at or bad at? It's possible that you are not aware of yourself much and you compare yourself to other people and that's why you feel like this. PS. I don't mean to sound hateful. I just have seen a very close friend fighting with his self-esteem issues. And he was completely unable to deal with this stuff because he claimed that "I'm not even self-aware, how I could have issues with self-esteem?"
hehehe. I do get self-conscious when my jokes bomb.