Aw im sorry you feel that way, you're not on your own though. I've always felt the same, never felt good enough. When you've heard or felt it for so long its hard to break that habit even when you are trying your best.
You've done amazingly well,and you should be proud; you deserve it. In the end it doesn't really matter how long it takes to achieve something, its just getting there in the end and not giving up.

x