I don't know if it's the same situation, but I know my sister had years of stomach problems every time she ate.  She would have half a meal, stop, have an upset stomach and stop. 

Eventually she saw a doctor and they said to cut things out of the diet to see if they were causing problems - first dairy, then gluten (wheat) - eventually it was discovered that she had celiac disease where she is intolerant to wheat.  And if you think about the number of foods you eat that have wheat in them in some form - seriously, it's everything - that would explain why apparently everything gave her a stomach ache.

Now, granted, the situations may not be comparable.  Im just offering an example from my life...

Also - another friend was constantly in pain and actually ended up needing to get his galbladder taken out.  It's just a possibility...