Fusion Drive Mysteriously filling up

I have a 3 TB Mac Hard drive.

For some strange reason, it seems to be filling up. I have nothing running, downloading.

Everything on the HD is less than 150GB... including apps, photos, Parallels Virtual Machine (130GB).

I have tried re-booting. Not running the VM. Nothing helps.

Can anyone please tell me what's happening and any fixes?

Much thanks.

Note screenshot of me system...