First, your test result is definitive: there is no doubt you are infected with HSV-2. Repeat testing by Western blot is not needed.
It is not possible to say when transmission occurred. It could have been any time since your previous negative blood test. I don't think you can necessarily attribute it to the missing condom episode. If in retrospect you recall otherwise unexplained symptoms, such as a few days of genital itching or irritation that you didn't pay much attention to at the time, that might be a clue.
It is not possible that the infection was latent and only recently gave you the positive test result. Some people believe that stress can trigger outbreaks, although the science doesn't actually support this idea. But nobody has ever proposed that stress alters the body's antibody response to infection, which is what the blood test measures. It doesn't happen.
As to moving on and living with herpes, a brief response in an online forum isn't the way to do it. You need to start by reading about the disease; some reliable sources are listed below. Find a herpes-knowledgeable health care provider. The MedHelp herpes community forum is also a good place for ongoing advice; the moderator there can be very helpful. Most important, don't panic: almost everybody with newly diagnosed genital herpes is shocked and upset as you have been, but almost everybody comes to understand it's not the end of the world (and not the end of healthy, rewarding sex), with less life impact than you currently fear. Sometimes counseling is part of the solution. (Your anger shows, by the way. I'm not sure how inadvertantly leaving a condom behind is your husband's fault or why it should be the "last straw" in a relationship.)
Good websites for genital herpes information are those run by the American Social Health Association (www.ashastd.org); my former health department, where I wrote much of the herpes information myself (www.metrokc.gov/health/apu/std); CDC (www.cdc.gov/std); and the Westover Heights Clinic of Portland, OR (www.westoverheights.com).
I hope this helps. Best wishes-- HHH, MD
I will add that this was the Herpes Select test that came back over 5