You should go to the doctors immediately and have a piss test.
They can identify what is in your urine that is causing it to turn dark.
blood, protein, sugars, etc.
you could have a bladder infection (drink cranberry juice and other acidic things to help plus lots of water) or more severly you could have more severe kidney problems.
Kidney Stones - doubtful since you dont have pain... but
initial stages of acute kidney failure
bergers disease (IGA nephropathy)
diabetis
certain poisons including heavy metals (lead, mercury, cadmium)
Get this diagnosed before you have to spend a lifetime on dialisys.
edit,
If you are experiencing chills and weak or upset stomach, this is almost guaranteed to be kidney problems... Get to the doctors now.
<==== Previously had bergers disease.