What you are describing is the mechanism in the brain that gets triggered when the stomach reached a certain level to tell you that you are full. There are some people who this mechanism does not get triggered when the stomach is full and continue to eat. It tends to happen to people that are very obese.
unfortunately, there is.... but I dunno what it's called :(
I watch CSI a lot (working on Season 6 right now) and there was a case where the guy never felt hungry. His case was very severe, though, to the point where he had to be restrained... in the show he was let loose and he ate himself to death :(
I, too, rarely feel full, but nowhere near as bad as the character did...
if you're worried about how much you eat and not feeling full, I would talk to your doctor ASAP... what country are you in? If you don't have a doctor then maybe a clinic can help?
I kinda know where you're coming from...
Wish you all the best