It takes time to build confidence.

Sit down and hand write your strong points and then the ones that are lacking. Once you have that list ... Pick one that needs work and do it. No matter how awkward it feels just keep chipping away at it.

For example I use to have trouble going out to eat by myself .. So I just went and picked a place and sat down and had a meal, was it comfortable ? No ....Did I feel like everyone was looking at me , Yep, but I just kept doing it. It soon became a simple enjoyable thing to do.

You just have to face the things that are tough for you to do.. Bull by horns. Its hard work , but its like learning everything else takes time and effort.

Maybe seeing a Therapist for a while can help you find out what can help.