It's pointless to speculate about the source of something you probably don't have. You can address the source of infection if necessary after repeat testing.
Herpes testing is not usually done in pregnant women.
This was my only affair in almost 10 years of marriage therefore if I contracted the virus previously shouldn't my wife have it? I guess my question is, if I did have it before my wife and we had two children, shouldn't her doctor have caught it during the numerous checkups during her pregnancy?
Most like you do not have HSV-2. At least half of results in the range as yours are falsely positive when the person also has positive result for HSV-1. A repeat of the same test might sort it out; if a repeat shows an ELISA ratio below 0.9, you can rely on that outcome and know for sure you don't have HSV-2. Or you can be tested with another test, such as the BiokitUSA test; if that is negative for HSV-2, you also can rely on the result. The last option is a Western blot test, available primarily at the University of Washington clinical lab in Seattle--most expensive (probably $200 including your local lab's blood draw and handling fees, and maybe not covered by insurance), but it is the gold standard for sorting out uncertain HSV blood test results. Whichever path you choose, I recommend retesting at about 4 months.
In the unlikely chance repeat testing is positive for HSV-2, it probably will mean a distant past infection, not from the extramarital affair you describe. Combining the near zero risk of HSV-2 from oral sex, low risk for any single episode of vaginal sex, still lower risk because of condom use, and the lack of symptoms of a new genital herpes infection, the chance you caught herpes from that event is near zero. It would almost have to be from some other source. This is why I would have recommended against HSV testing at all in your case. But now that you've started down that path and had the equivocal result, you should follow up with repeat testing as suggested above. While you await the outcome, relax: most likely you don't have it.
Good luck-- HHH, MD