My grandmother recently died and I'm severly depressed. How can I cope with this?

I'm 16 years old and my grandma was my best friend. She died from a failed liver and kidney transplant on easter morning. She seemed to have understood me more than anyone else had and I was very close to her. Almost closer than I am to my own mother. I feel like ever since she died, Just all happieness is just sucked out of me. I've been pushing away my friends, family, and even my boyfriend and I'm depressed like ALL the time. I need some advice on how to help my grandfather as well. He just lost his mom,brother and now his wife all in one month. If you can help me, I can really appreciate it. Thank you.