Sounds like the start of radiation systitus, which comes on gradually after radiation, had burning and frequency for 4 months until they found a tumor in the bladder caused by the radiation, removed tumor but bladder a real mess, went thru 80 hours of hyberbaric chamber that ended a month ago and feel great now, but remember radiation works for years after the treatments. The burning is from bladder Iritation and bleeding Have Doc give you a cystascope and find out what the problem is you will be glad you did. Don't be affraid of the systacope they sound much worse than they actually are.