with a long history of this, what kind of tests have you had? have you been diagnosed with any stomach disorder? are you on any stomach medications?
i would recommend you follow up with the further testing. it could be something as simple as gas pains or as serious as diverticulitis or anything in between.
there are a couple different classes of over the counter medications that may help with the symptoms of burning, nausea. there are the H2 blockers (zantac, pepcid) and the PPI meds (prilosec, prevacid). i would start with an H2 blocker to see if you get any relief.
knowing that certain foods make it worse, you would need to avoid those foods.
i agree about the appendicitis, it is not likely you have an acute case of this, but there could be some irritation there or it could be coming from the gallbladder (although that is not the usual area of pain for gallbladder).
in any scenario, i certainly do think getting follow-up with a GI doctor is the most appropriate thing for you to do. hope this helps!