What the is that burning sensation from?

well i did my first liver cleanse yesterday/today , i managed to flush out somewhere between 100-200 stones , some tiny specs,some size of peas and some almost a inch n length/diameter im guessing. This was on Dr. Clarks liver/gallbladder flush recipe. I was wondering about the burning sensation on the opening on my bowel , what is it from ? cuase its like almost unbearable like bad , is that the bile or some type or acid causing it? And how weak is a person supposed to feal? i been like exhuasted. What is the best foods for alil pcik me up or nutrients? I juiced this morning,fruit and had some squash soup.And another thing my foggy headedness is still there , do i need to do another flush in 2-3 weeks ? Or is it jus plain gunna take alil time for my body to regain its nutrients back again? Do i need more water ? thanx take care Je