Depression? What's wrong with me ?

I'm 16 and I do go outside anymore , I don't even go to school I had freinds but once they saw I wasn't coming out they stoped calling for me . I miss everything,parties ,funny moments just everything and its just depressing I hate living like this . I sleep all day and i wake up at noght in the dark somtimes sometimes and when I do want to go out it just dosent happen , I just end up sitting in home . I have no social life anymore . I just sit around the house , smoke and watch tv . And when I think about what I'm missing out on it depresses the **** out of me . I've been like this for a few months , also I have not eaten a full meal In a week :( what do I do? What's wrong with me? I cant remember the last rime i was happy I could go on for ages but this is big enough . Sorry about any spelling mistakes