I would recommend you to use OBS (Open Broadcaster Software). It is a free open-source software mostly used for live streaming but it can also record your screen.
Why I recommend it?
Nobody can notice that you are recording because it has no overlay over the screen. But, it still appears in the taskbar. (You can hide the taskbar, or change the icon, etc)
It does not affect the performance of the PC as much as other recorders. I used it a lot even in games and it is has better performane than Fraps, Action, Camtasia etc.
It supports Windows 7/8/10
Another suggestion is to use a software that takes screenshots every few seconds. That's what I used when I needed to track down my productivity when working. Most of the times, the applications that take these screenshots are hidden.
Link for OBS: https://obsproject.com/
And here is a tracking printscreen (open-source): https://github.com/ioanb7/TrackingPrintscreen
You can set it up in startup to run when the windows starts.