Here are a few things for you to check out
1. check what is running from start menu is their anything you dont recognise.
2. do a full virus scan
3. look in add/remove to see if their is anything you dont recognise that could have been installed at the same time as something else , change the top tab to sort by date.
4. Along the side of your list of programs you will see a tab somewhere on the right saying programs and features , windows sometimes puts things in this old style layout that does not go into add/remove.
5. run defender.
6. install and run antimalware bytes.
Have you used malwarebytes before. The reason I ask this is because you may not be fully aware of how Malwarebytes works. Infections of any kind can be made up of many segments , if you clicked on anything it found before quarantining and deleting you might have seen it say something like joe bloggs pup 5 , this means that joe bloggs pup is made up of 5 segments.
This is the important bit.... Malwarebytes is one of the best programs around but it cant always get rid of all segments of something on the first scan/quarantine/delete. You must do repeated scans till it finds nothing.
Also try adwcleaner by the same company
footnote ... i stopped using facebook a long time ago because its easy to hack , i got faceboook .... somebody wants to talk to you messages which was strange because i had not even made my profile , i logged in on my spare pc .... could not get in until i did forget password ( somebody changed it ) , i got recover password email to get into facebook and discovered somebody had made a massive profile that was not me , thats how easy it is to hack