People tend to notice what's different. Would it help to have a joke all ready for them? If they ask why you're in a wheelchair, say you're working on your upper body strength or something. That will put them at ease and show them the absurdity of their question and let them know you aren't comfortable pouring your heart out to strangers.

Maybe find a fully bumper sticker and put it on your chair. Let people know there's no reason to stare. Sort of a nothing to see here folks. Move along.

People also think they can put their hands on pregnant women's tummys.