Take a tablespoon of ES and see if the pain goes away. The dose can be repeated if necessary. If you can, an enema or colonic would be very beneficial to help clear out the colon.
I like to take a psyllium twice a day a few days before a flush and for about a week afterward. It helps me to absorb toxins and keep my bowels moving quickly. Adding Bentonite would be real good too.
Make sure you drink plenty of fluids, expecially water to rehydrate yourself after a flush.