The problem with low self-esteem is that you can compare yourself to the monstor from the pit and still find yourself lacking.
I recall, from my time in nursing, reading an article describing some therapy for people with low self-esteem. It described how such people should be encouraged to say to themselves, things like, I am a valid person. I have needs and wants that are important. Stuff like that. Someone got paid for that c**p, so I suppoe there was something positive.
Your self-esteem takes a tumble when all those aspects of your life become worthless. In my case, it was the realisation that I wasn't evil after all, my whole family really did hate me.
The only way to build yourself up again is to start from the bottom. However much it hurts, and it really does, you have to accept your situation and build your own life from there.
I am really sorry that I can't suggest a way you can take matter from your current situation. But to use an annalogy, your current situation is build on air. It has no foundation.