Irritable Bowel Syndrome (IBS): This condition is characterized by abdominal pain, changes in bowel movements (such as soft stools), and the presence of mucous in the stool. It's a common disorder that fits the symptoms described.

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause abdominal pain, changes in stool consistency (including soft stools), and the presence of mucous. These diseases are characterized by chronic inflammation of the gastrointestinal tract.
Gastroenteritis: Viral or bacterial infections can lead to abdominal pain, soft stools, and mucous in the stool. The yellow color could indicate the presence of bile, which might not be fully absorbed due to the infection.
Food Intolerance: Lactose intolerance, gluten intolerance (celiac disease), or other food intolerances can cause similar gastrointestinal symptoms, including abdominal pain, soft stools, and mucous, due to the body's inability to properly digest certain foods.

Appendicitis: Although appendicitis typically presents with severe abdominal pain, nausea, vomiting, and fever, atypical presentations can occur, especially in the early stages. It's crucial to consider appendicitis due to its potential for severe complications if not promptly treated.
Intestinal Obstruction: This is a blockage that prevents the normal flow of the products of digestion (including food, fluid, and gas) in the intestines. Symptoms can include abdominal pain, changes in bowel habits, and potentially the passage of soft stools or mucous if the obstruction is partial.
Diverticulitis: Inflammation of the diverticula in the digestive tract can cause abdominal pain, changes in bowel habits, and potentially the presence of mucous or blood in the stool.

Whipple's Disease: A rare, systemic bacterial infection that can cause malabsorption, leading to changes in stool consistency, abdominal pain, and other systemic symptoms.
Giardiasis: An intestinal infection caused by the parasite Giardia lamblia, which can lead to abdominal pain, soft stools, and the presence of mucous in the stool, although it more commonly causes diarrhea.
Bile Duct Obstruction: Obstruction of the bile ducts can lead to changes in stool color (often pale or clay-colored) and consistency, along with abdominal pain. However, the presence of yellow stool might not be the best fit for this diagnosis unless the obstruction is partial or intermittent.