Started taking amoxicillin 2 days ago for sinus infection. stools normally come out number 5 on bristol stool chart. now formed and in 1 piece. why?

Stool change antibio: It is common for the consistency and frequency of bowel movements to change when taking antibiotics. Antibiotics kill some naturally occurring bacteria in the intestines. This change in the balance of bacteria in the intestines causes changes in stools most common causes diarrhea but it could also cause less frequent and firmer bowel movements