Daily life thinking

I had my first child at 19 I'm 21 now she just turned 2 yesterday. I am in a new relationship n also has a 2 yr daughter. We will be together a year n July. He wants another baby but our toddlers are babies themselves. Yes I have baby fever every once n a while but how do I know if the time is right to have my 2nd child which would b his 3rd?