This is more than just a behavioral problem, it is an issue with his mental health. Just taking away privileges and home schooling him will not fix this.
You need to take him to be seen by a Pediatric Psychiatrist to be evaluated and get him in to see a therapist on a regular basis. He probably has clinical depression, which is absolutely treatable, but it won't go away by itself (in fact, it'll probably just get worse if left untreated).
Until he is evaluated, you won't know whether he needs medication, but if medication is suggested, it is imperative that he is closely monitored by a Psychiatrist and that it is coupled with therapy. Don't take him to his primary care physician and just accept medication. That typically causes more problems than it solves.
If he is resistant to seeing a therapist, you can start off by presenting it to him as family therapy. That way he doesn't feel like it's "all his fault" (particularly since it is not all his fault). It will also help you learn more about what is going on, and how you can more easily deal with things and, hopefully, reduce your own stress level.
If taking him to a therapist makes you worry about "what people will think", remember that not only is it no else's business, your son's life and your family are what matter. That's what you are working to save.
Good luck. It's not easy, but it will eventually get better if you get your son treated.
Debra :)