Mother's Day?

I guess every female is open to it, but on the second Sunday of each May, someone always seems to wish me a "Happy Mother's Day." But that's the thing: I'm not a mother. I'd said, "Thank you, but I'm not a mother," but eventually just shortened it to "Thank you." To get irritated is really just silly; how would anyone know whether I am a mother or not? When I told someone I wasn't a mother, she said, "Well, you're a sister or a niece or a cousin, and that's what the day is about." Really? Is it? Wouldn't that take away from the general idea? If it were about that, then it would be "Female Family Member Day." Hold on, let me email Hallmark and see what cards they can come up with. I bet you they could market it.
Beyond that, it makes me think. Do I really want to be a mother? I honestly don't know. Right now I know it's a no, and nothing can change my mind. No matter how many babies I hold or take care of, no matter how many cute pregnant women I see, it doesn't make me want to do it myself. And I do love children. I know it's entirely up to me, but why do I feel like this means there's something wrong with me?