In my opinion, investigations like kidney functions, blood sugar levels, ultrasound lower abdomen(already ruled out
kidney causes) ,intravenous pyelography , thyroid
function tests
and cystoscopy may be needed to confirm a diagnosis.I sincerely advise you to consult a urologist or nephrologist and get yourself evaluated so that a confirmatory diagnosis can be made.
Hope it helps.Take care and pls do keep me posted on how you are doing.Kind regards.