What Causes Odour In Vagina And What Is The Treatment?

I have a strong odour that comes from my vagina. I never use to have this, it is really in the past 5 years where it has got worse. I have been to the doctors where a smear test was done and also test for chlamidya and the tests were fine. I also had a urine infection and got antibiotics and that cleared up the smell too. I have also tried the balanceactiv gel and that cleared up for a short time only. How can I solve this?