I was VERY uncomfortable 6 hours after drinking the oil...sweaty, faint, nauseous, heart pounding...did pass lots of little "stones" the next day, followed by sludge. I felt very tired and worn out for about 36 hours and then felt GREAT! The "discomfort" was gone....for 1 night. Now for the past few days I have actually had MORE of this discomfort than before! My main symptom is GAS (flatus) and I have not read that in the forums here.
I did my first flush last weekend. I had the same thing happen 6 hours after drinking the olive oil. I broke into a sweat and felt faint. It passed quickly. The next morning I had only several tiny stones, but the next day I had more gravel-like stones and one larger green one. I too still have pain in my upper back and it did intensify during the day yesterday. It comes and goes. From my reading on this site two week intervals is suggested. Good luck.