My husband and I filed jointly, and we have a child to claim. We are under the wage limits but my check was only $900, and looks like it shouldve been $1700.... ???

You can make an adjustment on your 2020 tax return for stimulus payments you qualify for, but have not received. 

To do this in TurboTax, please follow these steps:

1. Enter the information in your return.
2. Click Federal Review at the top of your screen. 
3. On the screen, Let's make sure you got the right stimulus amount, click Continue.
4. You will be asked about the amounts of first round and second round stimulus payments you received. 
5. TurboTax will then calculate the amount of stimulus payment remaining that you are still entitled to.  This will show as a credit on line 30 of the 1040.

remember that the 2nd stimulus used the 2019 tax return only to determine what you are due.

But regardless, as noted, it will all reconcile on your 2020 tax return and any additional stimulus will be listed on Line 30 of Form 1040..... it will increase your refund (or reduce what you owe)