If our mortgage was never filed at the courthouse and we paid the property taxes but the ownership is still in the previous owner's name, how do I correct this?

Taxes are associated with ownership and so that means that the deed is in the former owner's name as well, and that is a real problem here.  Please bring all your paperwork to an attorney to review and help.  What you need to do is go down and get a copy of the deed on file as well.  You need to contact the mortgage holder and find out where the original is becuase when it is paid off you will need them to file a satisfaction.  Good luck.