Ah, yeah, the eye roll. I know it well. It bothered me a lot at first, but you'll get used to it.
When you tell people you're pursuing med school, do so with confidence. Brush off the negative responses. The best reaction I've gotten thus far is from my friend who's currently in dentistry school.
As for family members, I understand that, too. My parents, aunts, uncles, etc. didn't show much support at first. Use that as motivation. Prove them wrong. Let your actions do the talking.
"People can't do somethin' themselves, they wanna tell you you can't do it. If you want somethin', go get it. Period."