Weird, I too am 19 and have really sharp stomach pains when i don't eat for about 3-4 hours. I am usually always hungry but as of lately i haven't had much of an appetite but i get these pains regardless. If i try to eat, i can never have much before i start feeling sick.
I'm under a lot of pressure lately, could it be stress?
I've also been getting migraines pretty frequently too, i don't know if that relates.