Why do I not care about myself?

Okay, I'm 15 years old, and a freshman in high school (sounds a little ridiculous I know) Anyways, for several years I have been slowly losing interest and care about anything and everything in life. This unintentionally started when I was in 4th grade, I began to slack off in school. I ended up having to repeat 8th grade, and during the second time around I had a really rough year, my apathy eventually got the best of me, and I ended up going to jail for 2 weeks, a psychiatric hospital for 2 months, then I was placed in a residential treatment center by the courts and the juvenile probation department for 5 months. I got out back in November, and was doing well for awhile, but suddenly my apathy took control once again, and I feel powerless. I am failing every class in school, I'm about to repeat my freshman year, I have no self respect, my self esteem is in the gutter, I feel as if I'm not good enough for anyone, and I always have to prove myself. In the end I always end up failing though, I'm at the point where I'm possibly about to go back to jail, and fail my freshman year, at the SAME time, and I STILL cannot find the motivation to improve my life. Occasionally I have thoughts of suicide, it seems rather appealing at some moments. I honestly have no idea what to do, it feels like my life is going absolutely nowhere..