Hi. Thanks for your query. Noted the history and understood your concerns. Chantix can cause diarrhea as it has direct actions on the intestines and in fact all over the body. Stopping Cigars also can have direct positive or negative effects on intestines. But it is necessary to see for the routine causes too hence I would advise you the following: Get the stool sample tested for three consecutive days. Also blood tests particularly for liver and thyroid functions. If there is an evidence of an infection better to get the proper antibiotic cover along with probiotics. If there is no exact cause found or other tests like ultrasonography and colonoscopy are normal then I would think about IBS that is irritable bowel syndrome as a possible cause and would ask for control of anxiety and/or stress to be controlled.