None of HIS business!

Hey girls! Can anyone explain to me why (& maybe from experience) why my ex (who i have a 5 year old with), who is moved on and has been with another girl for almost 2 years, keeps questioning me about being pregnant? I am having another baby with someone else, i tell my 5 year old because who wouldn’t and my son has mentioned it one time before because i never said anything to him to not say Anything, but now every time my ex gets our son which is like every other month he questions our son and then confronts me about it Examples: He’s asked if i am Has told me i need to prove to him by taking a pregnancy test and showing He’s now asking to confirm about the name of my child And i know it’s not my son talking about it, my ex is the one that is questioning him. I keep playing it off because it’s none of his business and we have different lives but in my head i don’t understand why he cares If hes been moved on and why he can’t leave me alone not only about this but in general and go be happy with the other girl…