It seems the reason Derek gulped you up so quickly was because she was really hungry. Within seconds, your body starts to feel softer. The walls move around rapidly and her stomach acid rises above your stomach. The speed of the walls causes the acid to be splashed over you at random parts of your body which only aids in the process of digestion. You soon start to feel smaller and your legs have just become a mess of flesh. Your upper body would soon join them. Before you know it, you entire body has sunk in his digestive fluids and has become a goopy mess. This is when you pass out.