Regarding this issue, kristocontin is right as usual about WATER.
As a supplement to 8 glasses of water a day (its best to always have a large water bottle with you at all times - but watch out this may speed up your metabolism, you may wanna look into something to counteract this - raising your body's PH will make you more constipated though...)
stool softner+laxitive+lots of fluids
PhreeX is definately right about coke not being a good long term solution, but stool softener (docusate sodium) is NOT safe to take long term. It is essentially a detergant which irritates the bowel until you have to crap.
The only laxatives which are safe to take longterm are the magnesium based ones. I highly reccomend Magnesium Sulfate as its cheapest, just dump a shitload (pun intended) into a water bottle, and have that be your dedicated "going" water bottle. Just sip on this (with a chaser) every 30 minutes until it works. Any form of magnesium will work, such as Magnesium Citrate, Milk of Magnesia, or even the Magnesium Oxide pills "for joint health" or whatever. All magnesium also has the side benefit of helping your jaw while on speed. The Magnesium Oxide pills will eventually throw off your stomach PH (too high) if you take too much and make you more constipated, so take them with a Vitamin C tab, or alpha lipotic acid.
I also reccomend what my pharmacist "reccomends" (automagically printed on my RX) "fiber laxatives". Just buy a box of that super high fiber (says so on the box) bran cereal. It tastes like cardboard, but is kinda good with milk and chocolate chips.
In the early 1900s superstitious people believed that all forms of illness came from constipation, and so "regular clensings" were commonly prescribed by doctors. It was latered that having a weekly colonic and being "regular" don't really fucking (mmm fucking) matter. But some stupid people still believe it.
Also if you have a problem with bleeding, I highly reccommend using lube, and the dildo idea (remember NO DILDOS WITH SEAMS) could be beneficial too, just don't go too deep. If you bleed too much, its probably hemmrhoids, and no you aren't going to die. If you are really paranoid, check to see if the blood is in the stools or on the exterior, this will help comfort you that you aren't internally bleeding. If you are, you probably wanna go to the hospital.
So there ya go
the 3 pillars of crapping: water, fiber and magnesium.