If you have been experiencing stomach problems for 3 months without any known cause, it is important to seek medical attention to determine the underlying cause and receive appropriate treatment. Some possible causes of chronic stomach problems include:

1. Gastrointestinal infections: Certain infections, such as Helicobacter pylori, can cause chronic stomach problems.
2. Inflammatory bowel disease (IBD): IBD is a chronic condition that causes inflammation in the digestive tract and can cause symptoms like abdominal pain, diarrhea, and nausea.
3. Food intolerances or allergies: Certain food intolerances or allergies can cause chronic stomach problems, such as lactose intolerance or celiac disease.
4. Irritable bowel syndrome (IBS): IBS is a chronic condition that affects the large intestine and can cause symptoms like abdominal pain, cramping, and changes in bowel movements.
5. Stress or anxiety: Chronic stress or anxiety can cause digestive symptoms, including stomach pain, bloating, and diarrhea.

It is important to speak with a healthcare professional, such as a gastroenterologist or primary care physician, for proper evaluation and diagnosis. The healthcare professional may recommend tests, such as blood work or imaging, to determine the underlying cause of your symptoms. Treatment may include medication, dietary changes, stress management techniques, or other therapies depending on the underlying cause of your symptoms. Early diagnosis and treatment can help improve outcomes and reduce the risk of complications.