One extreme to another (full or starving).

Hello,
I have a strange question and I?m wondering if anyone has a suggestion. When I?m eating meals I have to stop when I?m still hungry because it takes 2 or 3 hours for the food to either reach my stomach OR for it to register in my brain that I?m over-full (don?t know which it is). I?m not talking slightly full -- I?m talking Thanksgiving Day full. This has been going on for the last 3 or 4 years. The doctor said I?m OK since he did all the tests (thanks). After feeling uncomfortably full for 1 or 2 hours I'm immediately starving again (no in between state). I don't understand how a person can go from extremely full to starving without an in between stage. Any suggestions on where to begin?