My tax return was rejected because it said I couldn't file twice but I hadn't filed under my social security number more than once anyway to fix this?

No.  You cannot fix a SSN rejection.    If you have checked to make sure you are using the correct SSN, then it is possible that someone else has accidentally (or on purpose) used your SSN on a 2021 tax return.   You will not be able to e-file this year.  The IRS will sort out the SSN issue, but you have to paper file for 2021.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.