Itching burning urethra with frequent vaginal infections

Hi. I've had this ongoing problem for two and a half years now. Initially I thought it was an STD and a homeopath said he'd picked up Chlamydia but no other urine or blood test tested positive. I've had every blood test in the book and all tests have been negative (it's very frustrating), changed my diet for candida, acidity etc had loads of antibiotics for the infections as well as two cystoscopies and a hysterectomy all to no avail. The itching and burning continues despite any of the above, it's like a crawling burning feeling in my urethr which is generally followed by a gardnerella infection or turns to cystitis. I'm not sure but I think I swam in a VERY polluted river just before this all started. I live on Citrus Soda and cranberry capsules. I'm just about to start a long term treatment for parasites and see if that might be where the problem lies. If there is anyone with any kind of advice for this I would be very grateful. Dawn