Thorin, you're not alone. I'm another from a broken family, and then I lost my mum as a teenager. It was a very big learning curve....and a very quick way to grow up. I came to learn pretty quickly to make the most of the cards I had been dealt rather than dwell on what could have been, or how it might be. That was the way I dealt with my trying teenage years.
I can't disagree with any of the above posters about keeping busy and keeping other poeple close to you. Hobbies, sports, (both playing and watching), build a model railway/railroad for real. The list is endless.
At the end of the day, you're still a lucky fella. You have a roof over your head, you are fed, you have people, you can be full of life every day, and you're still young with your life ahead of you, and just the little things like having access to a computer....to use Trainz/TRS and the like, TV, music....you name it.
Compare the situation to the starving people in East Africa. They don't have a roof over their head, they are not fed, they don't have many to rely on for support, they can't be full of life every day - as every day represents a challenge and the chance of death through starvation and disease is high, they don't get luxuries like computers, music, TV and all of those little things we can take for granted.
Ultimately, you control your destiny, and I speak through experience. You also do need to help yourself first, then help/assistance/support from others will come. Just take the East African example above and remember how lucky you really are.
Cheers,
Simon