Im 14 girl and extremley depressed PLEASE help me?

well i started refusing to go to school about 2 yrs ago i go sometimes but i go through these stages where i get too nervous and worried about school and i just cant go..its not because im lazy because i get up do exercise and do school work at home that i got from the school so i could catch up and i cant do home school because my mum already home schools my brother my life is so bad right now my mum thinks im getting bullied and that someone wants to bash me because she mis read something on facebook and i explain everything to her and she still doesnt beleive that im not getting bullied my best friend in the whole world i think shes over me not been at school which i can understand but she doesnt know what im going through and i know that if i loose her as a friend which i kinda already have im only gonna feel soo much worse theres these girls at school im afraid they judge me and because i use to date one of there boyfriends now he's coming to my school and gonna be in the same class. i dont really have a social life anymore i never thought id be like this ive tryed smoking and my brother and mum aunty and every one keeps nagging about school but they dont understand and im NOT telling them ihave now resulted to cutting to relese anger and fustration and shame on myself when i think about loosing my best friend i cut its got so bad where now i relise that if i cut myself so bad and was gonna die i woulnt care its much worse than it sounds theres alot more to be told but i cant type it all like fights with girls not punch ons but talk fights on facebook im scared of going to school to them right now i hate my life i never thought id be like this what can i do? X(