How can I gain confidence in myself ?

well you're halfway there already by realising. ask yourself who is losing out most when you don't participate or have a go - only you. then imagine you are much older looking back on your life, consider how many opportunities you've wasted and how much others would have appreciated them and how many regrets you've got.stop thinking about yourself and feelings.

You have to believe in yourself, no one can do it but you.

Tell yourself that you can and you will.. let that be your mantra.