How can I get a flat stomach?

I don’t know why, but I have a feeling that something’s wrong with my body.
And how can I get a six pack? Will it take a long time?

Btw, I’m 13, 5’3, and i weigh about 108lbs (49kg)

http://img134.imageshack.us/i/57692850.jpg/

http://img34.imageshack.us/i/82698175.jpg

FYI: I hit puberty last year p=