Nausea/diarrhea/constant belching no matter what I eat or drink (even water) - have tried antacids/pepto/anti-gas meds with no relief?

See Doctor. There are many causes for your symptoms. You need to see a doctor to find the source of the problem so you can receive the right treatment to make you feel better. Some possible causes, irritable bowel syndrome, too much/too little good bacteria in your GI tract, ulcers, or an inflammatory bowel disease.
?ibs. If you have already been evaluated with egd/colonoscopy, as well as food allergies and sprue all negative - possibly ibs - consider antidepressants.