I have been sick with a sinus infection and today I got an antibiotic from the doctor. I then got diarrhea. Unfortunately, it is EXTREMELY painful, to the point of being intolerable. It feels like my anus has tiny cuts all over it and the diarrhea is acidic. It burns. Also, the diarrhea is yellow with absolutely no fecal matter, it is basically urine coming out of my anus. Help?