Do you know what kind of investigation you are undergoing? This is a Public Trust topic, so you could be low risk, moderate risk or higher.
If you filled out an SF-85, then it’s low risk and you will only hear if you are not deemed suitable for employment. If you have already been authorized to operate (ATO), then just go about your business. You may not even get an interview with a low risk screening.
If you filled out an SF-85P, then it’s a moderate risk public trust investigation and may or may not involve an interview with an investigator. And as with the low risk, you won’t hear anything unless you are deemed unsuitable so if you’ve been cleared to work, then just continue.
I will say that in a position I’ve been working since Oct 2017, we filled out our SF-85P forms and started getting our interviews in the Spring of 2018. Mine was June 2018. The investigation was closed end of September 2018 - almost a year since submitting the E-QIP. I’m still working and will continue to do. I could ask my FSO if a suitability determination was made, but there’s no point. If I’m not suitable, they’ll be sure to let me know.