What Causes Persistent Lower Back Pain And Blood In Urine, Kidney Stones, And Ongoing Symptoms For Over 10 Years In A Young Man?

My son has had some blood in his urine since we first were told at age 14. He is now 24. He has had kidney stones since a teen. Lately he was seen for them again. The back pain never goes away. Some days when he is more active at work, or at the gym, it hurts more. Doctors shrug it off saying they see nothing wrong. The tests do not show anything and they say it is muscle spasms. Nathaniel has had over time, a CT, MRI and Xrays. Tonight he showed me a picture he took of the urine in the bathroom bowl, clearly deep pink. Does not hurt when he urinates, but Nathaniel still has his constant lower back pain. I am at a loss with the doctors. They suggested Pain Management. I want to find the cause of the back pain and blood. As I mentioned this has been ongoing for over 10 years now and just appears to get worse as time passes. Now with the gross hematuria, I am really concerned.