I only received 2 stimulus payments, should I have gotten 3?

Maybe.  There were 3 in all, but you may or may not have qualified to receive all 3.   Your dependent status (are you one or how many do you have) and income levels for tax years 2020 (the first two) and tax year 2021 (the 3rd one).    If you don't know what you have received, you can check your IRS Online Account. 

If you did not receive the full amount you qualified for, you can claim the recovery rebate on your tax return.   TurboTax will let you know what you qualify for, but you will need to know the amounts you received.   On this year's tax return, TurboTax is asking about the 3rd payment.   If you are missing any part of the first two payments, those are claimed on last year's taxes, 2020.