Why are you continuing to expose him to HSV2 without using a condom? Why is he playing "russian roulette?"  does he think he'll just take his chances?  The fact that the one test he chose to take is negatie can means (a) he doesn't have it yet or (b) the test is not sensitive enough or specific enough - and he may indeed have it.  IgG and IgM plus Biokit USA or Western blot to confirm the test he took as being reliable are some testing options.

If you both really understand HSV2 then you should be concerned enough for his health future to try and help him avoid exposure as much as possible and that means protected sex at all times.  If he does get it and you cross expose each other - you can increase the viral load (each of you, that is) and that is a poor health choice since it puts you at risk of more frequent recurrences of active virus.