Functional Dyspepsia: This condition is characterized by recurring episodes of upper abdominal pain or discomfort that is not explained by other medical conditions. The symptoms described by Terry, such as extreme gas pain in the rib cage and stomach, bloating, and relief with antacids like Mylanta, are consistent with functional dyspepsia. The fact that these episodes occur in the early morning hours, several hours after eating, and are relieved by Mylanta further supports this diagnosis.

Gastroesophageal Reflux Disease (GERD): Although Terry mentions that the pain starts under the ribs and then moves to the stomach, and he experiences bloating and gas, these symptoms can also be seen in GERD, especially if there is a component of acid reflux involved. The relief with Mylanta, an antacid, supports this possibility.
Irritable Bowel Syndrome (IBS): Given the bloating, gas, and abdominal discomfort, IBS could be considered, especially if there are alterations in bowel habits (though Terry reports regular bowel movements). However, the primary symptom of IBS is abdominal pain associated with changes in bowel habits, which is not clearly described here.
Stress or Anxiety-Related Symptoms: The episodes occurring in the early morning hours could suggest a stress or anxiety component, as these conditions can exacerbate gastrointestinal symptoms.

Peptic Ulcer Disease: Although less likely given the episodic nature and quick relief with Mylanta, peptic ulcers can cause severe abdominal pain and should be considered, especially if the pain were to worsen or not respond to antacids.
Gallbladder Disease: Biliary colic or cholecystitis could present with right upper quadrant or epigastric pain, especially after eating, though the timing and relief with Mylanta make this less likely.
Cardiac Ischemia: It's crucial to rule out cardiac causes of chest pain, even though the pain is described as starting under the ribs and moving to the stomach. Cardiac ischemia can sometimes present atypically.

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis are less likely given the intermittent nature of the symptoms and the lack of other typical symptoms like diarrhea, weight loss, or blood in the stool.
Gastric Cancer: Extremely unlikely given the young age and the episodic, self-limiting nature of the symptoms, but it's always a consideration in the differential diagnosis of abdominal pain.
Pancreatic Disorders: Pancreatitis or pancreatic cancer could cause abdominal pain, but these conditions usually present with more severe and persistent symptoms, and other signs like jaundice or significant weight loss might be expected.