Cystitis is making me miserable

I have been suffering in the past 18 months from cystitis (streptococus

bacteria in the urine most of the time).

I get infections every seven to eight weeks. I have a course of

anti-biotics, which clears it up for a while then I get the symptoms back

again.

I need to use the loo, sometimes every 20 minutes and I also get 'flu' like

symptoms. Sometimes I can not make it to the loo. I do drink well

including cranberry juice daily. What can I do to stop needing to pass

urine so frequently? It is making me miserable.