Low confidence comes from having insecurities, and insecurities come from resenting your flaws. If you can accept your flaws, your confidence will increase tenfold.
I’m confident because I don’t mind that my lips are too big and my hands are ugly and that I sometimes stutter and mix up words and that I’m terrible at telling stories. Sure, I’d like to work on the last two, but I don’t let them bring me down because I know that everyone else has their own list of flaws. Absolutely everyone. Even that girl with the perfect hair and lots of friends, and the gorgeous boy who kisses her softly. They’ve both got a list, and like almost everyone around them, they think that they’re the only ones. They hide their doubts well, but don’t be fooled. You are not alone.