Be sure you are taking probiotics or yogurt with active cultures as the antibiotics also kill the good bacteria that causes diarrhea. I found that the Z-pak (Zithramyacin) is the best for me. Got rid of my sinus infection fast. June idea - ask you doctor. This always happened to me with IBS before UC diagnosis. Actually, bleeding started after a double course of Amoxicillin. ElaineNY