1. Gluten Sensitivity (Non-Celiac Gluten Sensitivity or NCGS) (50% probability)

IBS is a functional gastrointestinal disorder characterized by abdominal pain and altered bowel habits without an identifiable organic cause. Your symptoms of intermittent abdominal pain, diarrhea, and bloating align well with IBS, and the gradual onset over a long period supports this diagnosis. The lack of blood in your stool and absence of significant weight loss to suggest a more serious organic disease also fits this pattern.

2. Celiac Disease (20% probability)

Celiac disease can present similarly but typically shows serological evidence (anti-tissue transglutaminase antibodies) and histological changes (villous atrophy) upon biopsy. Although the patient's normal blood work does not rule it out entirely, further specific testing (e.g., anti-TTG antibodies) is needed.

3. Irritable Bowel Syndrome (IBS) (15% probability)

SIBO, often an overlooked condition, occurs due to the abnormal growth of bacteria in the small intestine, leading to symptoms such as bloating, diarrhea, and sometimes weight loss. While your symptoms match this condition, the intermittent nature of your symptoms, the lack of malodorous stool, and the lack of a direct correlation to antibiotic use or history of surgery reduces its likelihood compared to IBS and celiac disease.

4. Other considerations:

Lactose Intolerance - 5%: Given the absence of dairy-related symptoms, this is less likely. Hypothyroidism - 5%: Should be ruled out due to nonspecific symptoms like fatigue and gastrointestinal disturbance. Small Intestinal Bacterial Overgrowth (SIBO) - 5%: Can mimic IBS and should be considered if other diagnoses are excluded.