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Your diarrhea could be a direct side effect of the antibiotic, in which case, it should resolve after stopping the antibiotic. It could also be due to a condition called Clostridium difficile infection (C. diff for short). C. diff is a bacterium typically found in the intestines of most people. But under certain circumstances (frequent exposure to antibiotics), a couple of strains of this bacteria can multiply and produce toxins (called C diff toxin A and B). This can provide diarrhea-sometimes bloody, with crampy abdominal pain.
I suggest getting tested for C diff. You need to submit a stool sample for C diff toxin. If it is positive, there are treatments for it includes oral Vancomycin, Fidaxomicin, or Metronidazole. I hope this helps.