Burden of other people?

Im 13 years old. I carry emotional burden of other people. I cant remember when it started but im getting really depressed and i need answers. I barely sleep at night,one day i feel down(most of the days) and other days im happy. And sometimes i just cry just for no reason at all. I be sleeping and wake up in the middle of the night crying thinking about a homeless man i saw he other day or people i see at school,streets,etc. I feel like i need to help their needs first then mines. All i think about people and society,everyday. Sometimes i just want to end my life,like i dnt belong here and im not needed here. I feel left out,depressed. I have low self esteem, and people don't want to talk to me because im shy,quiet,and boring. Well that what they say. I need help,advice or something to know that someone actually care.