Hi. Thanks for your query. Noted the history of taking Levofloxavin for a virus threatening to turn into pneumonia. You had bariatric surgery and took one tablet that might have caused diarrhea and spasms of stomach. Levofloxacin is not much known to cause diarrhea, although being an antibiotic can kill the normal bacterial flora also and cause diarrhea. I would suggest you the following in such a situation.: Get the stool test done and if the test is negative for infection adding on probiotics should help you. It may be better to stop the Levofloxacin and get started on another antibiotic. It is possible that there is an infection of the intestines and adding an antibiotic may be required, although Levofloxacin is a good antibiotic for intestinal infection in most of the cases. Thirdly, It may be a stomach flu and symptomatic treatment may help you the best. Hence get a clinical evaluation and investigations under the guidance of your treating Doctor to get the proper diagnosis and treatment.