There is no need to do another HIV test at 6 months. The Jan 13th test would have given you a final result for the exposure in August.
The ROCHE Elecsys Combi HIV test is an HIV antibody/ antigen test, which measures any HIV proteins in the body as well as antibodies. We find that these 4th generation tests would give you a final result at 3 months after exposure.
Let us know if you have any more questions or concerns.