Gastric Ulcer: The patient recently had an upper GI endoscopy showing a gastric ulcer, and the symptoms of epigastric pain, especially sharp pain that is episodic and moderate in severity, are consistent with a gastric ulcer. The pain is relieved by antacids, which further supports this diagnosis.

Gastroesophageal Reflux Disease (GERD): Although the patient does not have typical symptoms of GERD like heartburn, some patients can present with epigastric pain. The relief from antacids could also suggest GERD.
Peptic Ulcer Disease (PUD): Similar to gastric ulcers, duodenal ulcers can cause epigastric pain that is sharp and episodic. The recent endoscopy focused on gastric ulcers, but PUD could still be a consideration if the duodenum was not thoroughly examined or if there are multiple ulcers.
Functional Dyspepsia: This condition involves recurring signs and symptoms of indigestion that have no obvious cause. The patient's symptoms of epigastric pain without other significant gastrointestinal symptoms could fit this diagnosis, especially if the gastric ulcer is not the sole cause of the pain.

Myocardial Infarction: Although the patient denies chest pain, myocardial infarctions can occasionally present with epigastric pain, especially in women or diabetic patients. It's crucial to consider this diagnosis due to its high mortality rate if missed.
Pancreatitis: Acute pancreatitis can cause severe epigastric pain that radiates to the back. Although the patient does not have typical symptoms like vomiting or abdominal distension, pancreatitis should be considered, especially if there's a history of gallstones or alcohol abuse.
Cholecystitis: Inflammation of the gallbladder can cause right upper quadrant or epigastric pain, especially after eating fatty foods. The absence of fever and vomiting does not rule out this diagnosis.

Gastric Cancer: Although rare, especially in younger patients, gastric cancer can present with epigastric pain and weight loss. The recent diagnosis of a gastric ulcer increases the importance of monitoring for any changes in symptoms or signs that could suggest malignancy.
Zollinger-Ellison Syndrome: A rare disorder characterized by excessive gastric acid production leading to severe peptic ulcers. The patient's recent diagnosis of a gastric ulcer and the presence of epigastric pain could warrant further investigation if symptoms persist or worsen despite standard treatment.