False Negative for Herpes (& pregnant)

[Kim013]

I am 35 years old and just about nine months pregant and went in for my weekly ultrasound.  My doctor noticed a small bump that was open and asked me about it.  I remembered feeling something when I was in the shower and bathing, but just thought it was a pimple.  She cultured it to be safe and it came back postive for Herpes 2.  Needless to say, I was rather shocked.  I've never been diagnosed with any venereal disease, and had been tested for Herpes early on in my pregnancy (a blood test) as a routine precaution and the test came back negative.  My husband of four years has also been tested prior to us getting married and he came back negative as well.  I'm getting another blood test, as is my husband, but is it possible that the culture is false?  My OB-GYN didn't seem to think so.  I'm just really floored.  I've never noticed any significant "bump" or lesion ever, except for the occasional pimple, but maybe it was really a herpes sore???  I'm just really confused and in shock.  My doctor said that it is possible that I had such a low level when I had the blood test that it didn't show up.  It just makes me extremely nervous given that I'm about to give birth and the potential effects this can have on a baby.  She put me on Valtrex till I give birth to prevent any sort of outbreak. Any thoughts on how this could happen?   How likely is it that I had a false negative blood test early in the pregnancy?  A false culture?  (I have no question about my husband being unfaithful.  He's in shock as well.)