You might want to be tested for SIBO (small intestine bacterial overgrowth). Symptoms of SIBO include bloating, abdominal distension, abdominal pain or discomfort, diarrhea, fatigue, and weakness. There is a simple test for this which entails drinking a solution and then exhaling into a series of tubes every 20 minutes for three hours. (It can be done at home.) The lab checks for hydrogen and methane in your exhaled breath. You can read more about it by searching sibs on PUBMED, article PMC3099351.