You need to invest in some Magnesium Citrate and use it daily. It does the opposite of what opiates do to your intestines: draws fluid into them.
It's a much healthier alternative to any lexative. You can take a big dose of it and you'll go in an hour or two. Taking consistent, smaller doses will ensure you go regularly like a normal human being.
Besides being a laxative, it also is an awesome relaxing agent. Magnesium in a proper form is an amazing tool. I'm glad to see more users mentioning it nowadays in these type of threads.
EDIT: Natural Calm is a good quality Magnesium supplement if you're looking for some laxative action. There's no extended release like some other Magnesium supplements that try to combat the absorption/diarrhea issues of Magnesium. It is imperative that you get the Citrate since Oxide and other forms of it are mostly shit.