If you can't poop even after taking laxatives, then you may have a medical condition called slow transit constipation (STC). STC occurs when there is a delay in moving waste from the colon into the rectum. This causes hard stools to form in the colon instead of soft, normal stools. If you experience frequent episodes of constipation with no improvement after trying to change your diet, fluids, and activity levels, talk to your doctor about this possibility.