“When should I go to the ER for esophagitis?”

Well if you are 100% sure it is esophagitis(which is not a certainty unless an upper endoscopy proves it to be the case), then the major indications to go to the ED are 1) unremitting chest pain despite the use of appropriate medications(ie--PPIs or other effective antacid drugs), 2) upper GI bleeding, 3) inability to swallow or food getting stuck in the esophagus, and 4) any uncertainty about the diagnosis--as a symptom like chest pain could be due to another serious malady like a heart attack