I totally understand about self esteem being so dependent on other people's opinions. I'm the same way and it's really hard to not let it get to you. But yeah, when there's people on the internet being anonymous, that's just a recipe for cruelty; it's terrible.
It won't happen overnight, but you can become self-confident enough to not let other people's opinions affect you. Just try to love yourself [I know it's hard, I'm still trying too] and do what you want to do and relish in the freedom of finding yourself and connecting with your childhood and having fun and dealing with what you need to deal with, and try to remember that the people who don't matter, really do not matter.