How do become self confident?

For all you women out there, how do you become confident in yourself?

I’ve been self conscious since I was a super little kid and honestly I’m not too sure why. Well I am, but at the same time who really cares right? I am extremely shy because I’m always afraid of what others think. I’ve been told that I’m pretty and kind and a good person, but whenever I’m talking to someone I always get the impression that they don’t like me. And if I am “so called pretty” then why did it take me so long to get a boyfriend? Can people feel low self esteem?