What if I don't want to be Muslim? I'm 11 years old.

There is no pressure on you to be a Muslim, Islam teaches that there is no compulsion of religion. Your parents, however, do have a right to bring you up in an Islamic environment and teach you in accordance to Islamic values. If you choose not to believe in that, then there is no obligation for you; indeed, at the end of the day, Allah guides whom He wills (2:272). Of course, remember that Allah only enters believers to Paradise and enters disbelievers into Hellfire (which contains other, more horrific punishments in addition to the agonizing fire), both for eternity.