If there are loans that are not yours and you know nothing about on your credit report, it sounds like you have had your identity stolen. You should file a police report and dispute the information with the credit bureaus.
As far as protecting your tax information, you can elect to receive an identity protection PIN(IP PIN). This is a six-digit number that prevents someone else from filing a tax return using your Social Security number.
Here is an article regarding the PIN you may find helpful: How do I get my 6-digit IP PIN?