Magnesium citrate
"I've been feeling blocked up not getting everything out for two weeks, and for the last two days nothing but liquid is coming out, so I'm assuming fecal impaction.  Since I was still passing gas, I figured it would be okay to try out a laxative instead of just popping stool softeners with water.  I took half of the bottle at 8:30am, then figured if it's worth doing it's worth doing right so I drank the other half at 9:00.  It's 5:00 in the afternoon, and still nothing.  I figure I'll take some more softeners tonight, and head out to the pharmacy for tomorrow's preparations.  If I can't get it out between another bottle, glycerine suppositories, an enema, some vaseline, and a pair of XL latex gloves, then I think I'll have to go to the doc."