Children of Addicted Parents and People

I am only 13 but for as long as i can remember my life has been very different to that of my friends. I live alone with my mum. I have no brothers or sisters and I don't know where or who my dad is. It scares me when I see my mum drunk coz she can become really violent and unpleasant. The only people in my life that have been able to try and help me cope with this are my grandparents. I love them both so much but worry how this is effecting them. I went on holiday with my grandparents and my mum just 1 week ago. on that holiday my mum and grandma had a massive argument (my mum was drunk) which resulted in us going home early. at the moment i am staying with my grandparents. Today (the day i wrote this) i came home from school to find my mum drunk. She started being really horrible and saying she hated me, she even hit me on the shoulder. i love my mum and dont know what to do. please help.