You can still file for 2020 even though you were a stay at home mom. You do not require income in order to file. You would require certain types of income in order to be eligible for certain credits (ex.: the Earned Income Credit).
Many folks have yet to receive their 2019 refunds. I am pretty sure that you mean "mailed in my return last year" when you say "mailed in my refund last year", which is why I am letting you know the status of many tax payers. I, for example, had to file an amended for 2019. My 2019 originally filed was accepted on February 14th of 2020, and I then filed my amended on the 22nd of February, and it still is saying "in process".
For the second stimulus payment you state you have not received, as well as the additional stimulus for your new baby, you would inform the IRS of these two on your 2020 tax return. Here are the locations for each:
How Do I Get My Second Stimulus Check - TurboTax
TurboTax Tips for New Baby In 2020
