Please help me? I don't know what to do...?

I am a 14 yr old girl i dont even want to go to school because of the people i thought were my friends decided to make my bestfriend tell me that they didnt like and that i should move to a differnt lunch table, i have friends no one really knows what goes on in my life my mother died when i was nine in 2006 on mothers day night im not sure what she died of i just know that we didnt have much money and we were on welfare for mostly my whole life and that the night of morthers day i was sleeping in the same bed her i and my sister and my brother slept in a seperate room because he was a boy he was 13 i bet this effected more on him than me . my father has been in jail basicly for my life i might have seen him a month or so he is not a great inflence on my life he did drugs ,stole, was crule to my mother when he was living with us for a short period when i was very young around 5or6 years old .when my mother died we had no where to go so my grandmother took coustity of us. the time my "friends" decided to tell me to leave was the day after may 15 which was the day my mother would have died. i was so shoken up by this. my brother has turned to drugs and ciggerttes, my sister lives with her aunt now cause she used to live with her father he was and alcoholic as well as my mother (my sister has a differnt dad) her father got drunk one day didnt come home to jaime(my sister) and was found on a streat corner passed out because of too much alcohol intake. my sister started to cut herself. my grandparents know about my brother smoking i just hope they dont kick him out it make me cry just to think of it. he hasnt been doing well in school either .my grandmother says i have it so good here but id rather be broke poor like living with my mother , i was happy then. now everything is just upside down i put on a fake smile everyday and hope for the best but i will probally end up crying myself to sleep. my grandparents dont know how i truely feel they wouldnt understand i dont want to tell them i need help i dont want them to know because they will just judge me . my grandma is always telling me that im "im not as thin as i think i am " i am thin im not fat at all its just that they are always staying stuff like that. i just want to fit in. i am an a-b average in school i dont know how i can bottle up my feelings anylonger. people think im weird because i talk alot. i only talk to cover my emotions.i have nobody no one cares. i just dont know what to do ive tried my hardest not to turn to drugs and ciggeretts but they help my brother and my life is a mess , can someone please help me or give me some advice. please i am serious this isnt a joking matter i dont know what to do anymore.