Get a colonic. I'm serious. This guy at my gym lost 8 pounds getting one and has had no plumbing problems since.
One of my friends also got one after being irregular for a long time. She lost 4 pounds and says everything "comes out so smooth" now. She takes 2 Fiber Choice tablets every day, too, to make sure everything is "moving" properly.
I, too, have gotten a colonic, though not because I was irregular -- I just thought it was a good thing to do. I figured, "I have 22 years of crap in my guts!" I only lost 1/4 lb -- MAYBE -- but it DID leave me feeling refreshed, lighter, and I could suck my stomach in to a REALLY gross extent. It is not uncomfortable, either; more than anything, it just feels like you have the runs for 45 minutes.
Borntobefine mentioned magnesium citrate; that is also an excellent idea.
Good luck and happy pooping!