When my son was 3 weeks old he had hernia surgery. When we went back for a follow up I mentioned to the Dr. about how hard it was for my son to go poop. Come to find out that his rectum was to small. She had to dilate it. She showed me how to do it, which is not a pleasant thing but it helped him. I know this sounds gross and all but it worked. And also changing formulas can cause stool problems.