How can I tell in TurboTax if I need to pay estimated taxes for 2019? I thought I paid the full state taxes for 2018 & 2019 but my estimated taxes show as due, as well.

You'll need to estimate taxes based on your current income situation for 2019. Your estimated tax due for 2019 would not show in TurboTax 2018. Refer to this article for more information on estimating taxes: 

https://turbotax.intuit.com/tax-tips/small-business-taxes/estimated-taxes-how-to-determine-what-to-p...

You may also find this tool helpful for calculating / forecasting your estimated taxes: https://turbotax.intuit.com/tax-tools/calculators/taxcaster/