It's hard, and doesn't happen overnight. You have to build your self esteem step by step. The first step is willingness to treat yourself with respect, at least as well as you would anybody else. You can build self-efficacy and confidence and mastery by doing things or learning things that you can do well, and recognizing your abilities. You have to cheer for yourself and encourage yourself, not put yourself down like you might have been taught to do.

There is a lot more in this forum. Try reading through what is posted here already. I'm working through a free online self-confidence course, you might look at too:

http://forums.psychcentral.com/showthread.php?t=87388