Gastroenteritis: This is often the most common cause of stomach pain accompanied by nausea and vomiting, typically resulting from a viral or bacterial infection. The symptoms can range from mild to severe and usually resolve on their own within a few days.

Gastritis: Inflammation of the stomach lining, which can be caused by infection, alcohol, or nonsteroidal anti-inflammatory drugs (NSAIDs), leading to symptoms like stomach pain, nausea, and vomiting.
Peptic Ulcer Disease: Ulcers in the stomach or duodenum can cause intermittent stomach pain, often accompanied by nausea and vomiting, especially if the ulcer is bleeding or perforated.
Irritable Bowel Syndrome (IBS): Although IBS primarily causes changes in bowel habits, some patients may experience nausea and vomiting along with abdominal pain.
Food Poisoning: Consuming contaminated food can lead to symptoms of stomach pain, nausea, vomiting, and diarrhea, often resolving within a short period.

Appendicitis: Although the pain typically starts near the navel and then moves to the lower right abdomen, some cases can present with more generalized stomach pain, nausea, and vomiting. Missing this diagnosis can lead to perforation and severe complications.
Intestinal Obstruction: A blockage in the intestine can cause severe abdominal pain, nausea, vomiting, and constipation. This condition requires immediate medical attention to prevent tissue death.
Pancreatitis: Inflammation of the pancreas can cause severe, persistent abdominal pain, often radiating to the back, accompanied by nausea and vomiting. It can be life-threatening if not promptly treated.
Ectopic Pregnancy: In women of childbearing age, an ectopic pregnancy can cause abdominal pain, nausea, and vomiting. It is a medical emergency that requires immediate attention.

Zollinger-Ellison Syndrome: A rare disorder characterized by excessive gastric acid production due to a gastrin-producing tumor, leading to severe peptic ulcers, diarrhea, and abdominal pain.
Gastric Cancer: Although rare, especially in younger populations, gastric cancer can present with nonspecific symptoms like stomach pain, nausea, and vomiting, especially in advanced stages.
Inflammatory Bowel Disease (Crohn's Disease or Ulcerative Colitis): These chronic conditions can cause abdominal pain, diarrhea, weight loss, and sometimes nausea and vomiting, though the latter two are less common presenting symptoms.