Not a stupid question. There are none when it comes to PCa concerns. Prior to being diagnosed with PCa, I went to my PCP complaining of the same type of pain you are describing. She ran blood work at 7 AM. At 10 AM she called and said, " Thank God you came in for a blood test. You are in renal failure. Get to the emergency room now. They are expecting you."

I spent 3 lovely days in the hospital where they relieved the urine retention causing the renal failure (by foley insertion, of course). It took a few weeks to determine the urine retention was being cause by an enlarged prostate due to a grade 5 cancer. That was 6 months ago. I still self-catheterize to pee even after 4 months of ADT and a week of radiation. Not saying this is what's causing yours but, don't keep the pain a secret from your docs. It doesn't necessarily have to be caused by metastatic activity. Best wishes.