Clearle you need to test for peace of mind, you did not have a risk and do not need to test. I do, however, understand your need to do this because of the stress it is causing you.
Any generation of test (1st, 2nd, 3rd or 4th) can be considered conclusive and reliable at 12 weeks.
When you collect your negative result you really need to move on from this. Don't question the test, the window period etc...
You wil be negative, figure out how to accept it when you get this in black and white and stop worrying.
Dr.HHH or Dr.EWH never saw a negative test at 6 weeks turn out positive later and they are the experts in the field.
I would like to only understand...thats all.
you have been told REPEATEDLY...on this forum AND the expert forum...that you had NO RISK ! ! !