NOOOOOO!!!!
Don't ever ever ever say that!!
I used to be exactly like you... always mistaken for being significantly younger than what I am. I got married at 21 and when salesmen or politicians would come to our door (for YEARS) they'd ask if my parent's were home.
Then I had my daughter 2 years ago. I was 2 weeks from 28 and I honestly don't know what happened. I mean, I haven't been THAT sleep deprived in the last 2 years but I suddenly look EXACTLY my age. And unfortunately, that was 30 this year.
My skin got all crappy, lost a lot of its firmness, I feel like I can see every single poor now. My hair's got thinner and crappier too... it's so depressing! I have a LOT of gray hair too, though to be fair I've had gray hairs since about 24. My younger brother started getting them young too so it must be a hereditary thing.