BLOOD WORK, URINE TEST !!! ASAP
NEVER DARK BROWN, SOMETIMES IN KETOSIS YOULL GET A DARKER URINE BUT...
Do you have insurance? If not, you can go to a walk in md center. takes 20 minutes, shoul cost between 50-60 for the visit and 30-50 for the test. hey, $100 is nothing here, this si usally something you can treat quickly.
DO NOT let that go, serious irriversable damage could occur.
A few other people on this thread have givin you GREAT advice when suggesting blood/urine work.... get on it!!