Saturday I Woke Up Feeling Aching And Unusually Tired. Sunday

Saturday I woke up feeling aching and unusually tired. Sunday morning woke up with just aching in my back, but urine had normal color but had what looked like gray pus. Felt better by days end but still have gray matter in my urine. I am a diabetic, but has always been in control with medication. What is this gray matter? Kidney stones passing?