90% of people who have been infected with HIV will test positive between the 4 to 6 weeks after their exposure. A small percentage will test positive before that period and a small percent will test positive after. The closer to the 4 to 6 weeks period the more likely this small percent would get a positive result. Since you had a negative result at 86 days and unless you have been told you have a health condition that affects your immune system, you should be quite confident that your negative result is accurate.
For many people an exposure to HIV can cause a fair bit of anxiety and so testing at 86 days instead of 90 days may continues the anxiety. If you would feel better doing a test now that the 90 days has passed you can do so but be aware that this is merely to calm your anxiety and not because we would expect the test result to change.Please leave a comment to let us know if this answers your question or if you need more information.
For other readers, please feel free to leave a comment, or let us know if this was helpful.