If you took the HCV RNA by PCR test that tests for the actual virus and it came back not detected you do not have hep c. This test is valid a few weeks after exposure.
The HCV RNA test is normally only performed after a positive hep c antibody test to determine if the positive antibody result was from a previous exposure or a current infection.
For people with compromised immune systems like for those with HIV it could take as long as 6 months for them to develop enough antibodies to reach a detectable level.
The antibody test for healthy people at 12 weeks post a concerning exposure is conclusive.
Just to add the best person to ask is your doctor that ordered these tests.
We here are only patients who are or were infected with the hep c virus and not medical experts.
This is a community support forum and not constantly monitored for new activity. It could take a day or two possibly longer for someone to notice your question and respond.