Thank you for your feedback! Next time someone starts asking you when you are planning to have children, ask them if they are asking because they are planning on making a meaningful financial donation to fund the cause. When they say no, tell them that unless they are planning to offer legally binding monetary support, they have no right to express their opinion on the matter.
Some people have no boundaries whatsoever, but you shouldn't feel afraid to push back - it's none of their business. I also noticed that those who most actively advocate for having children often have nothing else going on in life, so it's kind of an excuse for them to make themselves feel accomplished (terrible reason #1).