Itaking antibiotics2weeks for pyelonephritis. I've just had horrendous cramps and urgency to pass stool. Mucus loose stool and some solid with nausea.

Need your doctor. Many antibiotics cause diarrhea, but the grave concern would be for an infection like c difficile- a toxin producing diarrhea. Your stool needs to be tested. Until you can be seen by a clinician yogurt MAY be beneficial.