Self esteem is just how you see your self. It does not depend on what others think of us, but what we truly believe about our selves. There are so many that have been beaten down to feel that we are not worth anything now, but again, this is not true. You are important. Don't compare yourself to the person next to you. Only compare yourself to how you were yesterday, last week, ten years ago, etc. As long as you are improving, then you are doing well.
You were brought into this world good enough and even if there is no one else in the world (which I seriously doubt) that can see this, you are still good enough. Don't accept less. I know a very homely girl growing up and she married a man that she didn't love because she never thought that she was good enough to get the man of her dreams. She was a beautiful woman, but she didn't believe she was good enough.
Value yourself. You are am amazing person and you deserve to be treated like you are a valuable person, not stepped on and abused. Be proud of who you are and what you can accomplish. Forget about the abuses of yesterday and move on. Learn from it and continue your journey. You are an amazing person.