I did 4 clark flushes last year, then had pain in the lower right of my abdomen... it was getting bad. I never did any colon cleansing after flushing. it turned out I had a stuck stone. I got it unstuck by taking castor oil every day for weeks, but the experience made me sick. If I had not got the stone unstuck, i would have been in horrible shape.
after that I always followed Andreas Moritz 's advice to ALWAYS follow a flush with a colonic or colema for this very reason. stuck stones happen, and they can ruin your health. I don't know if this is what happened to you, but it is a possibility. Enemas don't work well for this purpose, neither do p&b shakes. if you are still having pain, it could be a good idea to get a serious of professional colonics. And, post your story in the "ask andreas" forum if you can find it open.
Since your story sounds similar to what happened to me, I can't help but suspect that you have or had some stones stuck in your colon. the best (and only way i know of) to help this is colonics or colemas.