Why am i never full when i eat?!?

I am 13, I play hockey and softball. i can eat forever and i never get full! NEVER! i am 5'8 - 5'9 and i weigh 160 - 170.. so it's not like my weight is off the charts. I really want to know if it's like an eating disorder or something? also, i will eat, and if i get full, it's only for like minutes, then i am hungry again.. should i go see a doctor or something?