I’ve had kidney stones twice now, and "gravel" numerous times.  I can tell when they pass because I get a very sore back (the bigger the stone, the more severe the back-ache).  If it’s just gravel, the back ache is less severe, but I also have the stones/gravel bumble around in my bladder for up to several weeks.  I, too, went through many "negative" urine samples - there would be blood in the urine but no/very little signs of infection.  This seemed to baffle them for some reason.  Now that I know what it is, I try to drink lots (12+ extra glasses per day - ugh!) of water, and that seems to take care of it within a few days.  I recently went for an MRI to see if there was a stone stuck in my ureter (thankful there wasn’t), but the doctor DID tell me that I’m one of those "lucky stone producers", and put me on a LOW OXILATE diet.  He said that, contrary to popular belief, calcium intake has absolutely nothing to do with kidney stones.  I have a copy of the diet somewhere (which includes no chocolate, tea, nuts, peanut butter, etc.) that I could find for you, but you can find a copy of a low oxilate diet on the internet easily, too.

I sure pray that you can get to the bottom of this!!   This type of pain is worse for me than childbirth or gallstones, and I wouldn’t wish it on anyone, especially a child!  Maybe you should be seeing a urologist??  Praying for you both.