Although the most common cause for bloody diarrhea
after a course of prolonged antibiotics is C.Difficile recti on but in many cases Kleibsella Oxytoca bacteria has been found to be the main culprit for C.Difficile negative hemorrhagic colitis
Cytotoxins released by Kleibsella Oxytoca are the cause for bloody diarrhea.
In most of the cases the symptoms become all right in 5 to 6 days after stopping the antibiotics and giving intravenous fluids and oral probiotics.
Very rarely bloody diarhhea gets prolonged but the treatment remains the same.
Your doctor is absolutely right in his treatment and so have faith in him and abide by his instructions.