[smartpuppiepets]

It does sound like low sugar for me since the first post, i did not think of liver problems. Is the stool very very dry? Or moist and white? Some parasites can cause stool problems and not show in fecal exams, specially Gyardia. Do not be thinking that it can only happen to dirty places, i guess there are slightly different kinds of this nasty thing. I would deworm with "panacur-c" or "safeguard" for 9 days anyways, it will deworm and get rid of any gyardia or else. I have seen Gyardia cause white stools before, almost lost the puppy and did tons of fecal exams, by luck the last one did show the "thing" and this is what was prescribed that worked, by then my pocket was already broke with the vet bills. Anyways , this dewormer does not hurt and it is worthy to try i think.
Also have you tought about neurological causes? If so you will only find out after a few more weeks, But it is very similar to my story .... i would insist on this dewormer and take it from there. If it does not hurt ... worthy to try.
Good luck.