After a potential exposure i got a 4th gen hiv test done at 6 weeks, 8 weeks and 12 weeks and all negative.

Just out of anxiety and fear i got tested again from a different lab on 16th week and it was negative but value was 0.9 which is close to cut off value of 1

Again after 20 weeks i did another test from another lab and it was also negative and value was also very less. 

Am I in the clear sir ?

Your latest test result is just as negative as the previous ones. As long as the numerical value is below the positive cut-off, the test is negative. A higher number does not mean the test has detected a small amount of antigen, antibody, etc. It has to do with the sophisticated immunology and chemistry of the test. The very same blood specimen tested 10 times would give 10 different numbers, and exactly as you have found those numbers can be anything like 0.1, 0.4, 0.75, or 0.9. All are equally negative for HIV. (The test manufacturers intended the numerical results to be seen by tthe ordering physician and laboratory staff; the patient is supposed to simply be informed "positive" or "negative". Now that so many tests are requested by the patients themselves, they see details never intended. But they don't matter. You're definitely in the clear.

Anxiety is killing me everyday.

It's been almost 5 months since my last exposure and and I have taken almost 9 tests. Even though all are negative I am still not able to convince myself

That concludes this thread. Please note the forum policy against repeated questions on the same topic, especially when anxiety driven. This being your second about this exposure and your HIV fears and testing, it must be your last. Repetitive questions may be deleted without reply and without refund of the posting fee. The forum sponsor doesn't want repeated payment for questions already answered (or whose answers are obvious from previous discussions) and repeated answers tend to prolong rather than relieve anxiety. In addition, such questions have reduced educational value for other users, one of the forum's goals. Thank you for your understanding.