Hi, I'm not a medical professional but I do know that the window period to be confirmed as HIV negative is 12 weeks. This means that if you test more than 12 weeks after a risky encounter any test you do will pick up an HIV infection. The fact you tested 9 months after possible exposure means you can be completely sure you do not have HIV. Antibodies stay in the blood so even after 9 months a test would pick up an infection. Also -  after receiving a negative test after almost 9 months you can be sure that you didn't get HIV from the potential exposure in January. However, if you've had a risky encounter (I. E unprotected sex) in the last 12 weeks you'll need to test again after the 12 weeks are up. Also the symptoms of infection you get 2 to 6 weeks after being infected with HIV (swollen lymph nodes, fatigue, night sweats among others) only last for a few weeks so it would be highly unlikely for you to still have symptoms of HIV after 9 months. The symptoms go away a few weeks after initial infection and HIV becomes latent in the body for years without causing any symptoms. Hope this helps.