I had low confidence for a very long time and I did a lot of different things to improve it, many of them I can't remember, one of the most powerful was success stacking.

Everybody has been successful at something in their lives and everybody has successes everyday, people with low self esteem play these success down, it's time to stop this. Celebrate all of your successes, no matter how small, write them down everyday and review them everyday. Overtime this can help change the way you think about yourself.