keep that baby in there as long as you can!! ;) this is critical time for lung development! and remember, due dates are bogus; they are based on a perfect cycle in a perfect woman and lets face it, who IS that chick ?? no one has a perfect cycle, so naturally, rarely does someone actually have their baby naturally on their due date. remember, its called the ESTIMATED due date
it sounds like the symptoms you are having are well into getting ready for labor though! you could be a "lucky" one whos due date is later than baby will be ready. this could work to your and your baby's advantage; you dont have to be pressured into having your baby induced because you probably wont make it to your due date.
how it works is the lungs release a chemical when they are completed that starts labor. this way you ensure your baby is as ready as he/she can be! this is your baby and your body and the health of both of you; just relax, take it easy and your baby will come when he/she is ready! :) take slow relaxing walks, even making love if you are comfortable is said to help things along. but really, its those little lungs that make labor start! :) just wait for those lungs! its easier to adjust to a world outside the womb if you have got those good fully developed lungs ! :)
im sorry you are so uncomfortable though! dont worry, its only a little longer. i had to go to the bathroom (#2) all the time for aobut 2 weeks before my son was born. it was a "cleaning out" process. so dont worry, i dont think you have long to go.