What Happens when an overachiever stops being the best at everything?

I've been thinking a lot about why I seem to have hit such a long bought with depression because I know its whats been sitting in my way.  I used to be the kind of person that everything came easy to.  I made good grades and I had a lot of friends and I could charm anyone into seeing me as a happy fun person to be around.  Instead of being happy with myself I started to feel like if I couldn't keep that up no one would love me.  That if I wasn't the best at everything that I wasn't good for anything.  And then my dad took off and left me and my mother holding the bag.  At first I was able to keep at it, keep the grades and the friends and the achievements going but I started to put on weight.

Nearly 14 years later and I feel like all those things I was the best at are gone.  Every time I meet new people, instead of being that happy fun person, I'm the overweight braggart trying desperately to impress people into believing I still have some small measure of self worth.  Not surprisingly I'm the biggest I've ever been and I'm having a really hard time coming down in weight, so much trouble that I've been thinking about having surgery to correct my failure. 

So what happens to that overachiever isn't pretty.  I doubt myself in tasks I used to believe I was pretty good at, I have no love for myself because I feel like I've let everybody down by not being who they thought I'd be.  I ended up pregnant at 17 just like my mother, as she likes to point out every time I see her.  I've heard "you were such a smart girl and had the whole world ahead of you, why did you throw it all away," so many times it might as well be tattooed on my forehead. I live in a world I don't fit and I feel like I can't fit inside myself anymore. 

I'm trying to find a way to be okay with who ever I turn out to be and let go of the ridiculous expectations I had for myself a decade ago.  I want to think of it as introducing myself to who I'm going to be and see if I can get some of that spark back.  Somewhere in that charming girl who could do anything she put her mind to the real me existed.  I need to find a way to be okay if all those parts of her aren't there anymore.