Three month old baby? Was the baby born in 2018 or 2019?  If your child was born in 2018 make sure you said in My Info that the child lived with you the WHOLE year.  That way you get the child-related credits.  Of course, if he was born in 2019, wait for next year to claim your child on your 2019 return.

https://www.irs.gov/individuals/irs-withholding-calculator

The IRS is in the process of finalizing significant changes to Form W-4. 

When the new form comes out this summer, you need up select enough to cover your family, so at least 2. 

For more information about the new W-4, follow this link: 

https://www.fool.com/retirement/2019/04/10/heads-up-taxpayers-the-withholding-process-is-chan.aspx