Hi thanks for contacting HCM.... You have diarrhea since three week... Cause has to be searched for.... If needed stool culture done for choosing proper antibiotic according to causative bacteria.... Here I also want to rule out parasitic infection... Stool examination done... If egg of ameba or giardiasis seen then metronidazole given.... If it shows ankylostoma , ascaris , pin worm then albendazole needed... Maintain hydration with taking more water... Fruit juice taken... Avoid high spicy food , excess tea and non veg food as they irritate intestinal tract.... Probiotic tablet can be taken.... Avoid smoking and alcohol.... Take rest.... If still cause not clear then USG or colonoscopy needed for further work up. If colonoscopy dobe then biopsy taken to search for cause of colitis.. Take care. Keeping my suggestion in mind consult gastroentetologist..... Dr.Parth