What Causes White Bits Discharge In The Urine?

Occasionaly when I urinate, white bits of what I believe is calcium come out along with the urine, this hurts and stings alot and usually rends me immobile for a few minutes because the pain is unbearable. I am 17, white, male, Caucasian. I live in Romania and I m 100% sure that the next diagnostic these idiots issue me will be my last. I don t know whether these are kidney stones or some sort of calcium excess(i have been told i have calcium excess by some, and defficiency by others) or a completely different matter. There doesn t seem to be a pattern in these sessions, they don t appear immediately after consuming dairy products. I ve checked on multiple doctors and none of their suggestions or medicine helped. I m out of options.