Dont feel sorry for yourself.
Firstly, you must talk to your brother, if he scares you. Marijauna is very common these days.
You cant be afraid of a little pain. If you build you strength u wont get hurt so much. Start a sport. I assume you are a girl. Try tennis, its difficult, but u wont get hurt, and can get more demanding as your experience grows.
To get friends you have to hang out with people, learn from their reactions. Always be friendly, and if your not good, then be conscious of what u r doing to throw people off. Simply smile and talk, remember to try act normal. Also be yourself, this is what makes u unique, otherwise everyone could just as well talk to their reflections. People like being greeted, and being wanted. Dont stare or do creepy stuff.
Your family loves you. Dont leave this world, everything has its ups and downs. Smile !! For starters, get to know your brother better. Next call your dad and have a chat. Dont hate him, he is a person, imperfect and makes mistakes, try to understand him. Talk to you mum, what makes you sad and all. Also help out at home, ur mum must be a busy person. Enjoy life ! And everyone will try to share and bask in your joy with you =)