I have McAfee Total Protection. For my desktop which is on 24/7 it does a scan automatically once a week when I am not using the computer. My other computers start and run a scan when I have them on ( when it has been over a week since the last scan).
I use Windows Malicious Software Removal Tool too. You can find it under view update history in Settings>Update and security>Windows Update.
My suggestion would be to disable Defender completely and invest in a complete antivirus program. I have been using ESET for 20 years and have never been infected. BitDefender and Kaspersky are also good choices. Stay away from Norton/Symantec and McAfee.
I have to open with a caveat - although I haven't removed it from my system, I often think of it as Windows Offender instead of Windows Defender (now known as Microsoft Offender...I mean Defender). In my experience the best way to run a full scan was to set the Windows Power Options so the system would keep running all night, and start a full scan before going to bed....so I stopped doing it.
If you have not already done so, it might be a good idea to spring for a 3rd party security package.