Did this doctor do a ct scan of your kidneys looking for kidney stones or cysts?? I'm going through something very similar right now myself. I have excrutiating pain on and off on my left side, protein, and blood in my urine. No one can figure out what's wrong with me, i'm going to a urologist in a few weeks, so hopefully he'll have some answers.
Some more questions for you: do you have lupus?
Do you have a vitamin deficiency? (metallic taste in your mouth)
what kind of medications do you take?
Maybe we can figure this out together. Hope you find relief and some answers soon!