dear ..patient if your on antibiotic therapy diarrhea will be common is called antibiotic associated diarrhea. due to imbalance in the colonic microbiota caused by antibiotic therapy. Microbiota alteration changes carbohydrate metabolism with decreased short-chain fatty acid absorption and an osmotic diarrhea as a result. Another consequence of antibiotic therapy leading to diarrhea is overgrowth of potentially pathogenic organisms such as Clostridium difficile. It is defined as frequent loose and watery stools with no other complications. just consult your doctor he may advice stool culture ,endoscopy if needed. till that continue probiotics and tab metronidazole thrice in a day.