I almost completed my taxes a week ago. My son used my account last year. Today only his info shows up. How do I recover my tax return?

The TurboTax online editions can only be used for one tax return per account.  When your son's return was completed on the account it overwrote your tax return and your return is gone.

Go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript

For a fee of $30 you can get a complete federal tax return from the IRS by completing Form 4506 - http://www.irs.gov/pub/irs-pdf/f4506.pdf