Since you have filed a 2018 and 2019 federal tax return, there is nothing more that you need to do concerning the stimulus payment.
Go to this IRS website for stimulus payment information FAQ's - https://www.irs.gov/coronavirus/economic-impact-payment-information-center
Use this IRS website for stimulus payment status - https://www.irs.gov/coronavirus/get-my-payment
Use this IRS website for get my payment FAQ's - https://www.irs.gov/coronavirus/get-my-payment-frequently-asked-questions
I am worried about your reference to filing a "2018-2019" return. That would have to be TWO separate returns--a return for 2018 and a return for 2019. Did you prepare and file them separately on the forms for the specific tax years? Or did you combine the income from both years and put it all on the same tax return?