I’m trying to e file my return and it’s saying that it won’t file due to it being a duplicate return on my social security number but this is my first time filing so how can I find out

It could also be if you signed up on the IRS non-filer tool to give the IRS your Direct Deposit Info for the Stimulus Check.  If you did then see

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

Or are you claiming any dependents?  

You may be a victim of identity theft.

 See https://www.irs.gov/newsroom/taxpayer-guide-to-identity-theft

They indicate you should pay taxes due & file a paper form if you can't efile.  Then there is more to be done, but  see the  IRS's page above.

did you file a non-filers return to get stimulus?  that was the return that's causing the duplicate SSN number issue. then

Taxpayers who filed a non-filers return and now need to file an actual return for 2019 need to paper file an amended  2019 tax return with "Amended EIP Return" written at the top.

if you did not file a non-filers return you are either the victim of identity theft or a careless taxpayer who unintentionally entered your SSN by mistake. you too will need to paper file and include form 14039. in section B check box 1 and explain that some already filed a return using your SSN.  

Don't file form 14039 without understanding the implications.