If you're being bullied, it's not your fault and you're not alone. There is no justifiable reason for someone to bully you. And that includes mean text messages, mean tweets, posts on Facebook, email, any of that. Please tell someone. Find an adult that you trust: a parent, a teacher, a coach, a guidance counselor. Adults are the ones that have the power to stop this. Don't think that you have to handle it by yourself or keep it a secret.
It's really important to remember that a lot of bullying comes from fear, and ignorance, and insecurities, and is nothing to do with you as a person. Don't think that you've done something wrong or that, for some reason, you deserve to be treated like that.
If you see someone getting bullied, report it to your teacher. It doesn't make you a tattle-tale, but it's really important that somebody else knows what's going on. Nobody should have to be afraid to go to school, because they're worried about what someone is going to say or do to them.