Quit beating yourself up and instead, be honest.
There are things you're good at. There are things "everyone" are good at.
Find one, damned if others are "better" at it, and be proud of it.
Learn how to "act" as if you're the biggest, baddest, most intelligent man around. Learn to walk lie a king amongst pawns, and you'll be good, even if you don't learn how to be confident.