Definitely sounds like a UTI.
I have one at the moment, despite having good glucose control. The urgent need to pee is always how mine start, and if left to fester, then become painful.
Drink plenty of water - some advice I've had is to drink enough to make you feel sick... then you know you've drunk enough to wash out your system. And, of course, see your GP.
As for ketostix, I too got mine off Amazon. I go for the urinalysis ones with protein, leukocyte, glucose and ketone indicators. As I am prone to UTI's, I've found that testing twice a week can pick up an incoming UTI before I have symptoms. More often than not, lots of water and rest keeps it from fully developing.