Girls, please share your experience. My son has been pooping normally …

Girls, please share your experience. My son has been pooping normally about 3-4 times a day since birth, but we were prescribed Bactrim to regulate his microbiome. For 5 days, it was blissful calm, even without any diarrhea, but after stopping it, he stopped pooping altogether. He still poops easily, but cries when he wants to go, and sits for hours. I tried baby glycerin, 2 days of quiet again and then the crying went up higher. Today I put it in again. Will he get used to this? I follow a diet, eating so that his stool becomes softer, but nothing changes anymore for a week.