I've had four partners in my life and they've all been tested. no one has anything. so whys there an odor down there ?

Infection: There are numerous and many more common infections that affect the vagina and cervix and urinary tract that are not sexually transmitted. Your 'odor' is a symptom of an infection. It is not an STD.

You get chked: There can be many causes of odor from vagina. Sometimes a bacterial infection that may not show up in your partners. You should get checked if you have not already.