Do u suffer from a burning sensation when passing water?
You may have a touch of cystitis, I'm just assuming that you are a woman, I don't know why.
You can get off the shelf medicine (a sodium citrate based medicine) to treat this, most of it, however, does contain a touch of sugar, without it it would be fowl. The sugar is minimal, as most pharmaceutical companies try avoid using sugars in their products for obvious reasons.
If, however, you live in/ near a big big city you may be able to track down some citro-soda at some of the ethnic shops. This is not available in ordinary chemists and, be warned, contains no sugar and tastes fowl.
All that said, do not take these medicines if you are male. Go to your GP.