Rae, here's what I wish I had "gotten" at your age. People will have all kinds of expectations, about children and lots of other things. Just because someone has an expectation doesn't mean you have to fulfill it. Feeling pressured internally is always optional.
I am happily child-free by choice. Most of the time people who ask about children are just making conversation and they don't mean to be obnoxious. Here are the responses that I've used.
Q: Do you have kids?
A: "Only my husband!" said with a bright smile and a laugh.
Q: Are you going to have kids?
A: Oh, kids aren't in the stars for us. (smile and change topic)
Q: Are you going to have kids?
A: That ship has sailed! (smile and change topic--that works now that I'm older)
If people continue to question you, of course you get to shut them down. And of course you get to change your mind too! Big hugs.