Hi and welcome to Healthcare magic.
It is hard to say the origin of pain since there can be referd pain from any intraabdominal organ.the most commonly this is caused by
gallbaldder and pancreatic issue and you need some more specific tests such as CT scan
because US isnt good enough. To check you colon you should do colonoscopy
,but colon would manifest with deep and constant pain aggravated by food. Regards .Wish you good health.