The HIV window period is 6 months, but how long is that exactly? I tested negative at 24 weeks, 6 days (to be exact), but should I be concerned that I did not wait long enough?

you tested negative at 6 months then you are negative there is only a 1% chance that you could still be positive......it is extremely rare for some one to take that long to seroconvert, and usually that person already has a compromised immune system from drugs, serious illness...etc point is that you are negative and should no longer worry if you still have doubts you can test again in 3 months, but I would consider that a waste of time as most people test postive within the first month, and almost everyone tests positive after the first 3 months