Can any body suggest any way of getting rid of cystitis?

i have had some sort of water infection for 2 weeks now and i am pretty sure its cystitis. i am always getting water infections and with drinking plenty of water and cranberry juice they normally dissapear within a few days. not this one! blood in urine desperate urge to go to the loo, pain above pubic bone and pain whilst urinating. (the list goes on) i have been to the doctors they took a urine sample but have now asked me to repeat it. i dont know why. so thats another week! been told to drink cool boiled water with lemon juice. any ideas flutherites? desperate need! thanks