I am going to suspect it could be related to gallbladder/liver pain. Especially since you have a history of taking drugs and such. The Master-Cleanse detoxs the kidneys too and so it could very well be the kidneys. Keep up the cleanse until you can quit on a "high" but research the Liver Flush Forum here at the Curezone and plan on doing a series of Liver Flushes after you have resumed normal eating. I say this because your pain is on your RIGHT side and I experienced this on my 30 day flush. I was not too worried since it never got so bad I could not stand the pain and I was not ingesting solids but I knew without a doubt that I was a candidate for a good flushing afterward and it did take care of my pain.