Yes, stress and mental outlook is definitely part of it, I believe.
I noticed that you mentioned Depression in another post. I too suffered Depression in my early 20s - I was going through a very rough patch at that time, and even managed to develop an eating disorder.
Fortunately, those days are long behind me, however I believe the mental stress suffered at that time may be one of the reasons for my current health malaise.
Indeed, this is one of the points picked-up on by the experienced Ayurvedic doctor I had a consultation with. I'd never met the guy, hadn't told anyone my health history, yet a minute or two after reading my pulse was able to pin-point this mental suffering. Pretty incredible!
Anyway, back to digestion...
May I ask, after eating, do you ever feel a degree of tightness in your chest that almost restricts your breathing. Do you also feel the sensation that you need to burp, but that the automatic action/movement just doesn't 'happen'?