Pregnant and people looking at me like I'm crazy

When I'm working or see moms or moms to be i start a conversation and they always look at me like I'm crazy when I tell them I am pregnant I had someone come to the side of my register and look at me like I was crazy that it couldn't be true that I'm almost halfway what I think they aren't realizing is my shirt for work isn't form fitting as much as my regular shirts lol