What Causes Burning Sensation And Pain In The Upper Abdomen?

hello, i am 40 years male, i suffer cramping pain in the left upper abdomen and middle left abdomen burning sensation, i feel 3-4 days nausea, weakness, chills, my bowl change from that time. 2 days ago afternoon go to bathroom and clear urine, that time in one minute my abdominal pain gone. but still my bowl is not consistent. looks it not digest properly. my cbc is very good only MPV slight elevated. my urine r/e report normal. i feel still little week. one thing i am a thyredoctomy patient. 8 years ago i cur total thyroid. everyday take thyroxin. I feel now afraid colon of colon problem. please comments.