You must start from the inside, not the outside. I'd say. I'd dealt with a lot of low self estéem and thought that the earth would be a much better place without me.
As you, I have also felt alone and looked down upon. But then I started thinking that we aren't born in to this world as lower or better than each other. But we have a choice to impose good or bad to the world. To be part of it or to withdraw from it. If you choose to be part of the world and be good to the world, then you are of a great value to this world. Even little things counts. And this in itself should bring self-esteem. The negative option is easier but the other one is more than worth it! And no matter what your past is each time you bring a smile to someones face. Wether it's a deep smile or a shallow smile you are of great value to us all. Because we need each other. And people need you.
If you start thinking this way and doing good actions, I dare say it will not only affect you on the inside but also on the outside.
Best of luck!