think it may be kidneys , im almost sure
urine dark red/brown
have CAT scan in 2 more days
now getting sever pain in back
had fever, headaches , nausea for few days. away now
might be kidney stones
If you were in England, Scotland or Wales, I'd suggest calling 111 for advice. However I seem to remember that you're in NI, where 111 doesn't operate, so you should call the GP out of hours service.
If necessary, they can give you a hospital referral (which might save you queuing for hours in A&E) or even call an ambulance for you if they deem your condition to be an emergency:
https://www.nidirect.gov.uk/out-of-hours