Hi Jay.n, Although there is a possibility that a test present a false reading, false results are still very rare in occurrence and there are certain factors that increase someone's chance of receiving a false result. For example, if a user tests inside of the window period, there is a greater chance of them receiving a false negative result as it may be that they have not yet produced enough antibodies for the test to be able to accurately detect infection. Antiretrovirals are also another factor that can influence antibody production and therefore could possibly generate an inaccurate result. If you have performed 4 tests, all outside of the window period, and all 4 results have been negative then that is an extremely reliable outcome. The chance of someone receiving a false negative result is around 1 in 1,000, but the chance that all 5 of your negative tests were false is extremely unlikely, near to impossible I would be confident in saying. Your negative results are extremely accurate, reliable and can be taken as conclusive - meaning you do not need to test anymore. I would recommend trying to put this behind you and move on. I hope this helps. If you have any more questions please feel free to leave them in the thread below. Kindest regards, Becky