An antibody test done 4 years after the exposure is 100% accurate and conclusive. It positively rules out the possibility of the infection. You do not have HIV, trust your test report and move on with your life normally.
They are said to be inaccurate for false positives, a negative at your timeframe post exposure is conclusive as diver58 suggested.
You really are holding onto this unnecessarily. You do not have HIV.