My brother is ruining my life, what should I do?

I am 18 and my brother is 21. For my whole life (18 years) I have been tortured in my own home. My brother has been trying to rule over my life and he is not a normal person. He gets angry over stuff that normal people wouldn't get angry for and I'm sick of adjusting my life for him. I am on the brink of packing up my stuff and moving out. My mom is very loving and the only reason I stay is because of her. But I'm afraid its not enough for me to stay because my brother is and has been ruining my life, and its not good for my health or my nerves. I know my mom would break down in tears if I left but I cant take it anymore. And I've tried talking to my brother about the situation, but the only thing that happens is that he becomes good for a day and then after that forgets everything we talked about and goes back to being a jerk. Sometimes he just doesn't care what I have to say. What should I do?