Gastroesophageal Reflux Disease (GERD): The symptoms of persistent pain in the left upper quadrant, exacerbated by eating or when the stomach is empty, and a burning sensation, are classic for GERD. The discomfort during extended driving and when delaying bathroom visits could also be related to increased abdominal pressure.

Peptic Ulcer Disease: The pain pattern, especially the burning sensation when the stomach is empty, could suggest a peptic ulcer. The exacerbation of pain after eating also fits this diagnosis.
Functional Dyspepsia: Given the persistent nature of the pain and its relation to eating, functional dyspepsia is a consideration, especially if other organic causes are ruled out.
Irritable Bowel Syndrome (IBS): Although IBS typically presents with altered bowel habits, the discomfort when delaying bathroom visits and the exacerbation of symptoms by certain positions (like turning while sleeping) could suggest IBS, particularly if there are associated changes in bowel habits.

Pancreatitis: Although less likely, pancreatitis can present with persistent abdominal pain, especially in the upper quadrants, and can be exacerbated by eating. It's crucial to consider this diagnosis due to its potential severity.
Gastric Cancer: While rare, gastric cancer can present with nonspecific symptoms like dyspepsia and abdominal pain. It's essential to consider this in the differential, especially in older adults or those with risk factors.
Splenic Pathology (e.g., Splenomegaly, Splenic Infarct): Given the location of the pain in the left upper quadrant, splenic pathology should be considered, especially if there's a history of trauma or underlying conditions that could affect the spleen.

Gastric Volvulus: A rare condition where the stomach twists abnormally, which can cause severe abdominal pain and dyspepsia.
Intestinal Obstruction: Although the symptoms don't strongly suggest obstruction, it's a rare possibility that could present with abdominal pain and discomfort, especially if there's a history of surgery or other risk factors.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with a wide range of gastrointestinal symptoms, including dyspepsia and abdominal pain, although they are less likely given the description.