2 elisa tests for hiv done at 3 months and 6 months of exposure, is it a conformation that i dont have hiv if both tests are negative?

Almost certainly: The ELISA tests detect antibodies to HIV and can appear as early as 2 weeks after infection but, if not detected by 6 months, it's 99% certain that you haven't been infected. That doesn't necessarily mean you weren't exposed however, It could mean you were lucky. Stick with protected sex unless you are at least 99% certain your partner isn't infected either.