I had an endoscopy one month ago. they found redness of the mucosal layer in the stomach in 3 or 4 places. they did a biopsy and found no infection or precancerous cells. lately i have felt nausea and some burping. is this gastritis?

Gastritis should be detected by stomach biopsy and this condition is not always associated with H. pylori infection. Yes, your symptoms may be present in non specific gastritis. You should double check with your gastroenterologist for the definite diagnosis and treatment. Take care.

From your description, it is impossible to tell whether gastritis was present, and if it was, what the cause of it is. Your symptoms sound more like acid reflux than symptoms from gastritis, however. I would recommend you return to your G.I. Doctor for any further evaluation needed and to adjust your medications if necessary. Good luck.