Totally normal. If it isn't you can stand next to me. I've been with my husband for seven years, married 3 months. I've known since I was 12 that I didn't want kids of my own, and that was the first thing that brought H and I together.
We were always honest about not wanting kids, getting people used to the idea. When H had his vasectomy in the summer, we told our parents and not much anyone else. It wasn't their business. Since then, I tend to just smile and nod when people go on their baby talks. Usually, they're just reminiscing about when they were new parents, it often doesn't have anything to even do with us. But if they get pushy and rude, I bluntly tell them that the decision not to have kids became a permanent one back in July, so they can push all they want but it's a done deal.
Pushy strangers don't even get that kindness; I simply say "We can't have children". Boy does that shut people right up, and they should think we're infertile; maybe they'll think twice before getting into the face of someone who actually is infertile and sensitive about it.