Because you deep down want them to like you and DON'T want social humiliation. This puts tremendous pressure on you to perform, leading to avoidance and withdrawl. Which is a paradox, because to truly be comfortable you need to practice again and again and again...
I don't know. I do that too. Anxiety?
It could be two things:
It could be just that it takes most of us time to really develop our self confidence, and you're still young.
It could also be an anxiety problem, like depression or other. If we find ourselves limping badly, we go to a doctor. If you have anxiety, it's no big deal to get therapy - one of the best things i ever did. I could live with limp, but couldn't enjoy life until i resovled my depression.