For me, I've battled with BV for years as well. Luckily, for the past 2 months, I have had no symptoms of it... I will be doing a post shortly to update those that are still suffering. Just to hopefully shed a bit of light at the end of the tunnell.
However, each time I thought had BV and went to see a dr., they always did a culture right there in the office. He/she would take a sample and look at it under the microscope and let me know if it is or isn't BV. Of course it was each time and I knew it anyway before I went. I'm not sure why they are unable to do the same for you. Often times, they can do a whiff test (where they test the sample with some sort of solution (I belive a hydrogen peroxide solution) and it emits a foul odor which confirms BV). This is something that they are supposed to be able to do for you on the spot--I would think. If they are testing for STD's or something a bit more serious then sending it off to a lab is warrented. Believe me, its a struggle and there are no real answers or cures. The most I hear is, some women get it and some women don't. I feel for you and anyone else who is going through this. Good luck. You may want to do a search on this forum for BV or Bacterial Vaginosis. You'll find a lot of information and lots of remedies that some people try to battle theirs. Again, I wish you luck.