London Girl
BV is definetely more common, but not exclusive to, ladies who have multiple sexual partners (with or without a condom) even though its not actually passed from male to female (or vice versa).
Spermicides have been associated with an increased risk of BV so you're right, it is most likely because of the job we do, which was confirmed by Snake Lady anyway.
I've googled it and from what I can gather, a
possible reason that you keep getting BV is that the spermicide in the condoms may be causing the pH level of the vagina to rise which means that it becomes more alkaline and this causes the bad bacteria to multiply until the amount of bad bacteria in the vagina far outweigh the good. Treatments like Biofem and Bioactive are, to put it crudely, more acidic. So using these brings the pH level of the vagina back down to what it should be and restores the natural balance of good and bad bacteria.
If I were in your situation I think what I would do is get antibiotics again to clear it up quickly and then I would, as a preventative measure, use Bioactive or Biofem in much the same way as Cassie does in the thread mentioned below http://www.saafe.info/main/index.php?topic=2404.0 and see how you go with that. This is totally just what I think I would do, its totally up to you how you deal with it.

Also, woman using the coil have an increased risk of getting BV according to the sites i looked on in Google.
Good luck and let us know how you get on. xx