Musculoskeletal strain or spasm: The symptom of feeling better with bending back suggests a musculoskeletal origin, as this movement can help relieve tension in the abdominal muscles.

Gastroesophageal reflux disease (GERD): Upper abdominal cramping can be associated with GERD, especially if symptoms worsen with certain foods or positions.
Peptic ulcer disease: Although the absence of chest pain (CP) makes this less likely, peptic ulcers can cause upper abdominal cramping.
Irritable bowel syndrome (IBS): IBS can cause abdominal cramping and spasms, often relieved by bowel movements or changes in position.

Myocardial infarction (MI): Although the patient denies chest pain (CP) or shortness of breath (SOB), atypical presentations of MI can occur, especially in women or diabetic patients.
Pulmonary embolism (PE): Similar to MI, PE can have atypical presentations, and the absence of SOB does not rule it out entirely.
Aortic dissection: This is a rare but life-threatening condition that can cause severe abdominal or back pain, often with a tearing quality.

Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic abdominal pain and cramping but are less common than other diagnoses listed.
Pancreatitis: Acute or chronic pancreatitis can cause upper abdominal pain, often radiating to the back, but typically presents with more severe symptoms.
Gallbladder disease: Cholecystitis or cholelithiasis can cause right upper quadrant pain, which might be perceived as upper abdominal cramping in some cases.