My only advise is this: determine things that you are good at. It can be writing, cooking, coming up with unique ideas (thinking out of the box), noticing things others don't (attention to detail), drawing, playing an instrument, being good at video games.....whatever, and work on cultivating that skill. As you see the skill get better, and you see yourself making use of it, your confidence will also increase as well.

If it happens to be anything related to writing, I can give some exercises that may help if you'd like.