everyone has a time in there life when they feel like you do at the moment, i went through the same as you when i was your age. where it feels like the end of the world and that is made evern worse when you lose someone so close, and you dont want to go on without them. but we have to and with time it does get easier.
when i was 19 one of my very close friends was killed in a bike accident, my world fell apart going from talking every day to never hearing his voice or seeing his big grin again, i got to the point of never wanting to get up and i didn't want to see people, and then a month later my anutie died suddley and the three months after that my grandma died and then eight months after that my uncle died suddley and then a few weeks after that a friend from work was killed in a car crash, it got to the point when i didn't get up some mornings i was that down.
but then i spoke to someone who said to me, do you think all of these loved ones would want you crying and morning them still, they would want you to see just how quickly things can be taken away from you and you should live every minuet of everyday to the full, so then you have no regrets of not making the most of your friends and family coz there the people that matter dont push them away embrace them and live to the full.
one day you'll wake and look forward to the rest of the day, your still young theres so much for you to see and do. just go for it .
good luck