I really hate me life. What should I do?

story of my life: Okay first off, I am 15. Gender: girl. From the title, it seems like im a really negative person but I am actually not. I guess this depression started off 3 months ago. I go to a public school and I hang out with a small circle of friends (4 ppl). We all really get a long, we always laugh, we do everything together. On december, my bff (seriously best friend) i knew since 11 decided to move back overseas to her hometown. At first yeh know im really sad and everyones sad and we had a party and cried when she left. So when winter break ended, I had to go to school without her. At first, I always thought to myself: I still have friends, no biggie! :D . But I guess I was wrong. My other close friend got a boyfriend, and she has been the center of attention for almost 2 months. Every day, I get pushed around, left alone. I try to fit in by laughing with them even if its not funny. Then, the other friend who used to be in our group transferred schools. 2 other people decided to join my friend and I. Apparently, girl A likes to stick to my friend 24/7. Girl B and I kinda get along, we laugh and stuff together until recently she started sticking to my other friend just because she was getting attention a lot. Im tired of my school life. Everyday I get left alone not on purpose, but it seems like im invisible... since elementary till now, I never was popular or attractive or anything like that. I was always invisible to some people. I am chubby and short, but I guess im average looking (not flattering myself). But recently I started to hate Girl B for some reason. And at home, since my mother sometimes go so mad at me and spaz, I want to suicide. Girl B didnt do anything to me but I hate her guts. Whenever my mom yells at me, I dont interrupt her and after shes done I go to my room and cry my lungs out. I even tried opening the window and sitting on my window, deciding to jump off or not. I am christian and I love God. I know God sent me to earth to live. But I really hate this life. At school, people think I am positive and cute, but they dont know the true me. And recently everyday I cry while im in the shower. I sometimes think I really need to see a psychologist LOL. But I dont have that much of a problem. Also note, Girl B does drugs and she drinks a lot, but we dont get affected by her. I get really good grades too. ARUGH JUST THINKING ABOUT THIS MAKES ME CRAZZZY. WHAT THE FK SHOULD I DO WITH MY LIFE MAYBE ITS BETTER OFF IF IM DEAD. By the way those of you who read until now thanks for reading LOL. Please give useful answers, and not just some answers to make me forget all of this. I hate my life.