Could Black, Watery Diarrhea Returning After A Previous Infection Indicate I Need Antibiotics Or Further Evaluation?

Hi, I’ve had Diarrhea for about 2-3 months and when I went to the doctors and did a stool sample, they told me they found a bug. I hadn’t had any episodes after that so the doctor told me I should come back if it continued again and they would prescribe me with antibiotics. My Diarrhea has come back but this time the Diarrhea is black and watery.