What Causes Blood In My Stool?

I'll be 62 in a couple of days. In recent months, I've taken three Nystatin tablets daily to fight Candida Albicans. When taking this medication, I've seen blood within my stool. On two occasions, I had found red blood in the toilet (water was red). By the way, I'm seeing my doctor this morning. I saw a post on the Healthmagic site written by the mother describing the identical symptoms experienced by her child who was on Nystatin. Is that drug capable of causing internal bleeding? The maker of that drug said they've never heard of this before. But, as I said, my symptoms were identical to those suffered by this child. I saw the post yesterday...it's not there today. Perhaps it was another site.