Why have I lost interest in everything?

I'm a 16 year old guy and I have a few days of school left and I'm usually so happy but I don't even care. I have a huge fish tank cuz I love fish I but I haven't touched it (only to feed them) in weeks. I used to play with my dogs outside and don't anymore. My grades are falling I'm letting myself go. I used to shower every day and straighten my hair. Now I shower every 2 or 3 days and straighten it once until it gets washed again. I'm a ghost hunter and I have no interest in going on a ghost hunt. I've been eating far less. I haven't been getting good sleep. Nothing in particular is bothering me except for q few problems at home. I have braces and I used to clean then really well now I just brush then regularly and less too. I had a gf and I dumped her. I don't know why. I used to want to go out with friends now I couldn't care less about doing anything. Not even Facebook entertains me anymOre... I used o talk to ppl on there all the time now when someone posts on my wall I don't care to answer.... What is wrong with me? Btw I'm on my iPod, sorry if there's typos. Thanks .... /: