Symptoms of pseudomembranous colitis may include: 
Watery diarrhea.
Stomach cramps, pain or tenderness.
Fever.
Pus or mucus in the stool.
Nausea.
Dehydration.
 Symptoms of pseudomembranous colitis can begin as soon as 1 to 2 days after you start taking an antibiotic, or as long as several months or longer after you finish taking the antibiotic.