Also: the titers in antibody test don't necessarily mean you were "exposed" to a certain virus. For instance, my last HSV2 test was 0.58. I had a lot of blood tests for HSV2 that yielded similar results over the years. Yet, there's no evidence I carry HSV2, only HSV1 (results over 1.1).
Such blood test will very rarely yield a zero result. It has to do with the chemistry of the test. So you're test is negative for now apparently because not enough time has passed for you to build IgG antibodies. But as you antibody response solidifies, the test will most probably yield an above 1.1 result.
During the "window period" of the test (it takes 3-4 months for antibodies to rise), of course people might get false-negative results, such as yours. It's a flaw, but there's nothing to be done about it. It's a limitation of this test.
A positive culture with a negative blood test usually indicates that you contracted it in the last 3-4 months. You should pursue a new blood test within 1-2 month to check if your blood test will then be positive, meaning that it's a confirmed recent infection.
As for trying to pinpoint the source of your infection, it'll probably be a tough task unless you ask both partners to get tested specifically for herpes and actually see their results. Many people believe they got tested for herpes but it turns out they only had the usual STD screening, that does not include herpes I and II IgG. It would be better if both partners get tested 3-4 months after the encounter, because it might be a recent infection for them too.
As for the incubation period, it's actually 2-20, usually no longer than 3 weeks. But when we talk about incubation period we're talking about the time that it takes to show initial infection symptoms - such as multiple, bilateral sores. Many people don't experience such symptoms and might only notice them during a recurrent outbreak, which is usually milder. Makes sense? But as I said above, a positive culture and a negative blood test usually indicates that this is a new infection for you.