Good Grief.
Stop over analyzing and just live your life.
Confidence comes with experience. You can only be truly confident when you KNOW you can do something because you've successfully done it before, more than once.
Faking confidence will get you humiliated when you act like you know what you're doing, then screw it up because you don't and publicly demonstrate that you are a liar and an idiot.
You don't have to have confidence when you're doing something you're unsure of. You have to have HUMILITY. The courage to admit that you're not sure what you're doing, but giving it a shot anyway. Then if you look stupid when you fail the first time or two you can always shrug, blush, and say "Hey, cut me some slack, I'm new at this" that way you don't look like a jerk, you look like a decent person who doesn't take themselves too seriously and is willing to risk a little embarrassment to learn something new.
Its not rocket surgery.
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"Strange, inaccessible worlds exist at our very elbows"
- Howard Phillips Lovecraft