I always get full but there are only 1-3 bites left on my plate. Why does this happen?

First bite syndrome is a side effect of some surgical treatments for head and neck cancer that is thought to be caused by nerve damage. It can also be caused by a head and neck tumor itself. The syndrome causes pain in the mouth that is triggered by salivation or when taking the first few bites of food during a meal. The pain can be described as intense, sharp, or like a muscle spasm. The pain is usually felt in the parotid (salivary gland) region, which is in the back of the mouth close to the ears, and is usually only felt on one side. The pain lessens with each bite of food but will return if there is a break in eating. First bite syndrome can start anywhere from days, to months, to years after treatment. This side effect can resolve on its own, but there are some treatments that can be helpful for this side effect.

Explanation:

*sigh*

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.