It might be because of you genetics.Some families are small so their children get the genetics and that makes them small.For example I'm tall and im still young i got it from my dad's side of the family.But something that I think will help you be tall is playing basketball because if you see the players are very tall because when they want to dung the ball in the hoop they stretch.So maybe if you play basketball exercise eat healthy it might work.
Hope this helps =D
