His stomach pain (started 4 months ago) is waking him up in the middle of the night; a hot water bottle helps him get back to sleep. His endoscopy showed no signs of tumors, no acid damage, no evidence of Celiac disease, and a normal esophagus.He stopped eating grains for about 3 weeks. Stomach bloatiness has subsided. He stopped eating gluten for about 8 months. He has been avoiding coffee, alcohol, citrus foods, and spicy foods all summer.
What could be causing the pain?