I feel like my life has no meaning.?

I am 15 years old. I feel like I am just taking up space on this planet. I feel guilty of my family's wealth (we are middle cl, so we don't have a lot of wealth but I feel bad for the people in poverty that have nothing) I wish I could give them money but I don't get and allowance and I can't get a job and my parent's can't really afford to donate to charity because we have to pay off our car and vacations and stuff. I just sit in front of the TV and computer and eat and listen to my ipod when there are starving and suffering people all over the world. I wish I had something good to contribute to the world, but I don't think I do. I wish I was smart and could come up with a breakthrough medical treatment to cure diseases, the creativity to connect with people through music or art, or athletic abilities so I could inspire people and be a role model. Or at least I could be a person of good character to influence others but I don't have good character. What do I do???