What causes that feeling of being gassy or having a distended stomach after eating?

Aerophagia versus... Aerophagia (swallowed air) distends stomach & may result in burping. Also, gassiness/ stomach distension after meals can reflect: 1) partial gastric outlet obstruction due to gastritis/ulcer; 2) pyloric narrowing from scar; 3) gastroparesis due to delayed emptying of stomach (as w/diabetic gut neuropathy); 4) bacterial overgrowth in gut; 5) any malabsorption; 6) pancreatic maldigestion 7) lots more.