What Causes Spells Of Bloating, Belching, Constipation And Abdominal Pain?

I have been ill on and off for the past 4 months. I have spells of bloating, uncontrolable belching, upper stomach ache (like someone hit you in the stomach), constipation at times. I have had a colonoscopy/endoscopic and both were nothing out of the normal. Does the colonoscopy/endoscopic suffice for an upper/lower GI? Also, they now want to do gastic emptying study. Do you have any idea what the problem could be?