Stomach problem n gas. Me out of causes?

I am feeling heaviness in my right side of lower corner of stomach n incr after eating food n when am sleep n feeling almost all time heaviness having too much gas inside my stomach always sound come of gas from my stomach n feel like travelling throughout to my complete abdomen i did ultrasound of abdomen with KUB not having any problems like stone n all clear i did colonoscopy n endoscopy in which GERD endoscopy n multiple small ulcer in large intestine found thats why my digestive system is bad so my question is why i feel heaviness right corner of stomach is due to gas or acid imbalance or indigestion?? I dont have any bad habits like smoking n drinking never do this plz help me out of causes?? Thx