My screen keeps switching desktops without me switching it manually

Make sure Automatically rearrange spaces based on most recent use is switched off

in System Preferences> Mission Control.

Oh and you do not need any Anti-Virus protection, there are no viruses that attack the mac,

AV apps just take up system resources and slow your mac down, they can also flag up

files that it considers a threat, which may lead you to delete them. Quite often these

files are system files needed for the smooth operation of your mac.

Ok it may be a corrupt preferences file.

Click on your Desktop, click Go in the menubar select Go to Folder.

Enter this text,

~/Library/Preferences/com.apple.dock.plist

press Go

A new Finder window will open with the file highlighted,

move the file to the Trash, do not empty it yet.

Restart your mac, the file will be regenerated.

Open System Preferences> Mission Control and make sure that box is unchecked.

If the behaviour of Desktops/ Spaces is now working as you would expect, then delete the file in the Trash.

if it didn't try the same procedure but with this file,

~/Library Preferences/com.apple.systempreferences.plist

Create a new User with admin privileges, set up that account like the account you have with the same set up for Desktops/ Spaces, and set up System Preferences> Mission Control just as it is in the original account.

See if the odd behaviour happens in this new account.