I have diarrhea that is dark red and my stomach hurts.?

two days ago after work i had fever and my diarrhea started. i guess after drinking the water there which now i know it isn't clean water made me sick. i've been eating little amounts of food because i don't want to overload my stomach. since i had fever i though it was an infection in my stomach so i took antibiotics, but the diarrhea won't go away. even though i ate some food only dark red stuff has been coming out. i also took pepto and alkaseltzer to try to make it better and it is still the same. my stomach hurts and took some medicine for pair relivers and it goes away the first two hours.