Your post is pretty deep and valid (as a first post, whoa!) and yes, we are so accustomed to what others think of us we forgot to listen to what is truly inside of us. I too used to live in doubt all the time but I am in progress of freeing this poisonous anxiety that does nothing but harm.
I'm so happy someone really came to know what I actually wanted to express. It means a lot to me. :)
Yes, doubt gives you nothing except tensions and makes your mind unstable. Hope you get rid of this poison soon. And don't forget to introspect. :)