First, make sure you entered the Social Security Number correctly. If it is correct and your return is still rejected by the IRS, someone else filed a return using your Social Security Number. 

1. If you think your parents claimed you as a dependent, you can edit your Personal Info to indicate that someone can and will claim you as a dependent on their tax return. Then you can try e-filing your updated return. (Otherwise, your parents will need to amend their return to remove you as a dependent and you can mail your return to the IRS.)
2. If you suspect someone is falsely using your Social Security Number, please follow the recommendations in the FAQ below.

What to do if you suspect tax-related identity theft https://ttlc.intuit.com/replies/3301430