Just to add to what everyone else has said - keep drinking your fluids.
If you can get to Holland & Barrett (or similar, if they don't have that round your way), pick up some cranberry EXTRACT - it's got the active ingredient that's in cranberry juice, but you dilute it and it's got virtually no sugar in it, unlike regular cranberry or the cystitis sachets.
I had a UTI for about three weeks back in November, so I feel your pain. Try a sitz bath too - run a hot bath so if you sit in it, it comes up to your hips, then dump in a load of bicarbonate of soda into the bath water, get in and sit for about 10 minutes. The bicarb will neutralise the stinging (hopefully). These were my lifesavers when I had it!