I have a rash which comes and goes but is more often there than not. It presents as itchy, hard bumps under the skin but the itching doesn't last long. When the bumps shrink back down again (after a couple of days) you can pop the middle out of them but not squeeze like an acne pimple. What comes out is like a hard piece of grit or sand not greasey but solid and when you touch them it sends like a nerve shock through the skin.could this be to do with fybromyalgia or my kidneys ?