Gastroesophageal Reflux Disease (GERD): The epigastric location of the pain and its exacerbation by eating are classic symptoms for GERD. The absence of nausea, vomiting, and normal laboratory tests (including normal lipase, which rules out pancreatitis) further supports this diagnosis.

Peptic Ulcer Disease: Similar to GERD, peptic ulcers can cause sharp epigastric pain that worsens with eating. The normal laboratory tests do not rule out this condition, as peptic ulcers are often diagnosed based on symptoms and confirmed with endoscopy.
Functional Dyspepsia: This condition involves recurring signs and symptoms of indigestion that have no obvious cause. Symptoms can include pain or discomfort in the upper abdomen that may be exacerbated by eating.
Irritable Bowel Syndrome (IBS): Although IBS typically presents with a combination of abdominal pain and changes in bowel habits, the diarrhea this morning could be a part of the syndrome, and abdominal pain is a key feature.

Pancreatitis: Although the lipase level is normal, which makes pancreatitis less likely, it's crucial not to miss this diagnosis due to its potential severity. Some cases of pancreatitis, especially if chronic or in the early stages, might not have elevated lipase levels.
Gallbladder Disease (Cholecystitis or Cholelithiasis): The epigastric pain and the slight elevation in bilirubin could suggest gallbladder pathology, especially if the pain radiates to the right upper quadrant or is associated with fatty food intake.
Mesenteric Ischemia: This is a less common but critical diagnosis to consider, especially in older patients or those with risk factors for vascular disease. The presentation can be nonspecific, including abdominal pain out of proportion to physical examination findings.

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with abdominal pain and changes in bowel habits. However, they are less likely given the acute onset and the specific location of the pain.
Abdominal Migraine: A condition more commonly seen in children but can occur in adults, characterized by recurrent episodes of severe abdominal pain, often accompanied by other migraine features like headache or aura.
Intestinal Obstruction: Although less likely given the absence of vomiting and the pattern of pain, intestinal obstruction can cause severe abdominal pain and alterations in bowel habits.