After I purchased my order and was about to file, it shows me the tax return with my ssn has already been submitted. But I am 100% I only use turbo tax to file it. How come? And in this case what shou

If you used the non-filer site to get a stimulus check, you will now get a  "duplicate SSN” rejection.  We are seeing people who did not notice or ignored the warning on that site about using it if they would be filing a tax return.

https://ttlc.intuit.com/community/tax-topics/help/stimulus-how-to-file-your-return-after-getting-reject-r0000-902-01/01/1602609