The IRS still has not processed my 2018 tax return My previous employer did not report everything I earned. I have sent in everything they ask for do I file my 2019 still

Yes---send in your 2019 return.  if the IRS does not have your 2018 return for the stimulus check they will use 2019.   

And you can still sort out your 2018 issues.  What kind of income was it?  Was it on a W-2 or a 1099Misc?

It was a W-2 for my 2018. My previous employer did not give the irs all my income. So I had to send in a letter from them stating how much I made. The irs has been processing it for over a year and now with all of this they have no telephone assistance. I just don’t want the 2018 return to affect my 2019 return. Will it?