Do you ever have to wait a while, after you've eaten, to feel full?

I was awfully hungry about an hour and a half ago so I ate a small bowl of imitation crab meat, which I dipped in butter, then made a cheese pizza out of half an English muffin, tomato sauce and mozzarella cheese. I know that’s enough to fill me up, but I’m still hungry! But I don’t feel like eating. I know from experience I’ll feel full in a while, or at least I won’t be hungry any more.
Why does that happen sometimes?