I have been having stomach problems for almost two weeks now--loose stools and diahhrea, bloating, very gassy. Can glucosamine cause this?

Yes, but! . Glucosamine can cause this, but many types of arthritis can be associated with inflammation of the small intestine . You should try a course of sulfasalazine 500mg delayed release bid. If this works, you have an arthritis, albeit mild. Why are you taking glucosamine? It is of little or no value?