J.B.
Ouch! Did they specifically check for BV? It's a bacterial infection that can affect as many as 1 in 5 pregnant women. I would assume that between the test the ER and your OB did they would think to check for this, but I've had medical professionals overlook dumber things so I would call and ask if they tested and ruled that out.
If it's not that, then it sounds like a nasty yeast infection. Call your doc and ask if it's safe to use OTC yeast infection treatments while pregnant. I'm pretty sure that I had to treat a yeast infection during one of my pregnancies and that the OTC treatment was fine, but be sure to ask first.