I didn't go through all the comments on the thread, but so far what I've seen is just bullshit. People around here are reading too much the DSM (or going to the wrong therapist, pick one).
You have anxiety, OP? Good! Most of us have to deal with it. No, I'm not saying "stop it and cheer up!". It's a real problem, but doesn't need to be a problem that will make your life stop.
I went to a roller-coaster of emotions in the last 2, 3 years (from valleys of depression and anxiety to peaks of extreme happiness). I went through everything you said, the impostor syndrome is the fuckin' worst shit that can happen to someone. This train still hits me, sometimes. That's not easy.
How did I overcame it? Changing my thoughts. The impostor syndrome faded away when I realized that the people around me don't know what they're doing, too! Nobody knows how everything works and I'm still looking for answers about how the world didn't meltdown yet.
See? I didn't get any better changing my mind by saying that I'm good and I know what I'm doing. I got better because now I see that everyone are lost, just like me!
Fear of embarrassment? Learn to fix quickly what you did wrong. Nobody will notice nor will care if everything is working. And when you see that other people are lost too, as I said above, you won't care if you're good or don't.
At the end of the day, it's just you that matters. You don't need to proof you're good to everyone. You know that you're good because the point you've reached in your life.