Why can't I stop eating?

I ate half a box of Frosted Mini Wheats: Strawberry one by one. I started feeling a bit of an upset stomach so I stopped. I got this sudden craving for a grilled cheese. This isn't the first time its happened. I would feel full and get a food craving. I'm only 100 pounds for 5'2" also. So, I don't know what. And no its not that time of month.