I've been eating healthy but continue with persistent nausea, gas, and loose stools. Stools are brown but formless resembling aerated soil and sinks rather than floats. EGD, blood tests, CT scan, X-rays all normal. Diagnosed with mild gastritis.

Need to examine. It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity at tolerated.