What should I do with my life? Its just wasting away... 15 years have already gone.?

I'm 15, for 15 years I have done absolutely nothing. The world hasn't been effected by my presence in a positive manner. If I was killed as an infant the world would be the same as it is now. I feel that my lifetime is not enough to effect the world in the manner I dream to (don't worry, I'll do it positively). I guess I'll try to try, but simply succeeding in the things that I do is not enough. I want to express my opinions and have them considered and have them effect other's perspectives. I need to find a cure to cancer or something!! To change the course of the future by leaving a huge imprint on the present... I need to do something with my life, and I need to start now in order for it to actually do anything. I've wasted too much time already. I need motivation, an idea; I need to learn everything and anything and then stimulate and challenge the globe. Someone please give me something to do.