The advice from Curfew is correct so it is time to move on from hiv fears. Plus the duo was conclusive after 4. You had no hiv symptoms since you weren't exposed to hiv. Late seroconversion is a myth - especially when 2 people tested since it would have to be a double late conversion.
See doc if you have a health problem today instead of wasting any more time focusing on the wrong disease. Perhaps you have Covid etc.
No, the window would not be extended.
Any test you took at 8, 10, or 14 weeks would be conclusive.
What was your risk activity that you need to test for?