You don’t mention the typing of the positive swab – was it HSV 1 or HSV 2?
The Igg test misses 30% of HSV 1 infections so he could be infected and the test didn’t pick it up.
You say that you’ve been HSV 1 positive for 10 years and have had two cold sores. Had you received oral sex prior to 10 years ago? The IgG test misses 8% of HSV 2 infections compared to the blot, so it could have missed an HSV 2 infection. Yes, the blot would clear this all up, but let me know the type of the positive swab test.
It isn’t possible that it is a new infection for both of you – that makes no sense.