Teenageness is bloody well difficult. It *could* be just stress or hormones. However, the way you describe it, it sounds an awful lot like depression. Speaking as someone who's had depression since age 10, what you describe...sounds very familiar.
I would say, get thee to a counselor or therapist. If they diagnose you, you'll have options for treatment, and you can start doing things that will help you to live life more fully again. Even if they don't diagnose you with depression, counseling may help you adjust to whatever situations there may be in your life that are the cause of this stress.
The rule of thumb for figuring out if it's depression is the duration, by the way. If the symptoms of depression (crying a lot, unable to rouse interest in activities you used to enjoy, etc) last for more than three weeks (I think that's the "official" diagnosis criteria), then it's probably depression, not just hormones.
If you want someone to talk to about this stuff, feel free to PM me. I'm not too much older than you; I remember very vividly what it was like at 16. I hope you can find and get the help that you need.