I guess it's quite normal to think that one day you'll just magically figure it all out. Hint: You don't...
1. Confidence comes from experience - without doing something it's difficult to feel confident doing it. Think about snowboarding. Pretty much NOBODY is confident on their first try. Now do it for 10 years 10 hours a week, and your board has pretty much grown to be a part of your body. But you have to start at the bottom to get to the top.
2. Learning to try is an important thing to be confident about. You sound like you avoid trying things, because you don't feel confident in doing them. Therefore your don't become experienced (and therefore confident) with them either. Failing at something is not the end of the world, and you can actually have a laugh about it. My old aikido instructor used to say that if you never fail at what you do, you are doing something wrong. You sound as if you want to avoid things you can fail at (be judged, oh I'm not good at this, I bet everyone notices that. Well yes, they probably do and appreciate you putting in the effort to try).
I get this a lot too, going outside is a struggle (I am a night crawler and tend to go out when it's dark - during summers I struggle because there really aren't any dark hours and I usually use it to learn to go out like a normal person...), I fear that people judge me (how I look, what I wear, how I wear it, etc etc etc)... The truth is, it doesn't matter.
What kind of works for me (I still get anxious but I've learned to adapt and it does go away for a bit), is being clear as to what I like and what I want to be: I choose clothes I like, and do things the way I see fit - if someone disagrees, they are free to do things differently. If someone truly has a problem with how you do something that doesn't affect them, then in the end that tells more about that other person than it does about you.
"If you need a safe space, see a therapist" - Jordan Peterson