My son was born this year and my wife hasn't worked since 2019 do to pregnancy, she still doesn't work but she isn't qualifying as a dependent and I can't file for head of household. Why?

A spouse can NEVER be a dependent and Head of household is for *unmarred* persons.

What are you worried about, you simply file a JOINT tax return with your spouse even if the spouse has no income.    The deduction for joint is much better then either a dependent or HOH anyway.