I wish I could help somehow... I know exactly how you feel - I tried to kill myself once and now I'm ashamed of my cowardness. Life is an unique chance for all of us - a chance to feel, to dream, to be happy and even to be sad. I believe life was given to us and taking it away, even from ourselves is just like deliberately breaking apart a small present your parents gave you, a present they have bought with their last money because they love you, just to make you happy, just to make you smile... It's unfair!
Any problem has a solution and it's never self-injury. Aggression is hard to suppress, and it's useless. That's why you'd better find some hobby, better sport. Find something or someone to love - people are most miserable when they don't love, not when they are not loved by anyone...
Life definitely has a meaning, even though it might be hard to find. Don't do anything on the spur of the moment, you might be sorry for it one day.
The sun shines and although you might not appreciate it now, you know somewhere deep inside that it makes you happy.