Is This Why You're So, Um, Backed Up?
Why it's causing a backup: You've been using the wrong ones. Over-the-counter laxatives share the same goal of getting your bowels moving, but they don't do all it in the same way. Osmotic laxatives (like MiraLAX or milk of magnesia) work by drawing water into your bowels from nearby tissue, softening stool so it moves more easily through your digestive system. Stimulant laxatives (look for ingredients like bisacodyl and sennosides), on the other hand, trigger muscle contractions in your intestinal wall that move the contents of your bowels along. Using stimulant laxatives occasionally (think once per month) is fine; if you're taking them daily or every other day, you may find yourself constipated again once you stop. "Your body can become dependent on them," explains Neha Shah, MPH, RD, a clinical dietitian with Stanford Health Care, in California, so you may not be able to have a bowel movement without them.
How to fix it: Switching to osmotic laxatives, which don't lead to dependency, can help. If you still find it difficult to go, see a gastroenterologist, as there are stronger but non-habit-forming prescription laxatives you can try.