What you’re asking about something we call a “window period.”
The window period is time between potential exposure to infection and the point when the test will give an accurate result. The window period for the HIV test we use in Manitoba is 2 weeks to 3 months. This means that it can take up to 3 months for HIV antibodies to show up in the body, so we cannot rule out HIV transmission until 3 months after a potential exposure.
Since you report that the potential exposure was a year ago and the test you took was 6 months after that, we would conclude that your test results were conclusive. No need to retest because of that exposure a year ago.
The Manitoba HIV Program recommends that if you are sexually active, that you build routine HIV and STI testing into your health appointments once a year. You can do this with your health practitioner or at Nine Circles Community Health Centre. Of course, you can test more frequently if have unprotected sex with a new partner or multiple partners, or use injection drugs.
I hope this has been helpful!