Ok so I cheated and I am hungry

This past Saturday, I had a coke. Truth be told, it wasn't all that great. I working on cutting back on portion sizes but I am starving. This isn't psychological hunger. I am hungry. I just had two slices of pizza. My stomach is still growling. I think to myself, surely a small would be able to eat two slices and be satisfied, so what is wrong with me? Does the body look at colories or volume. It finished the pizza 20 miniutes and it is like I have eaten a thing. Does someone know if this is a result of stretching my stomach or do I have an unrealistic view of what average size person could eat and be satified with? My perspective could be off. I had a sandwich, chips and an apple for lunch, cereal for breakfast and I have been hungry throughout the day. This is a bunch of bull.