It sounds like you have two goals, generally speaking:

1. Feel adequate.

2. Do well.

It sounds like you are achieving goal 2. You are doing well, but you are not achieving goal 1. You still feel inadequate.

You explained why you feel inadequate. It has everything to do with your background. No doubt you understand that trying to make yourself feel adequate is a very difficult task, given that background.

I wonder if you could drop feeling adequate as a goal.

I wonder if you could focus on doing well on goals you want to accomplish--and tell the voices of inadequacy "there you go again, you are the endless background noise that I am not taking to heart."