Is it normal to someone call you a "baby"?

I'm 18 Y.O guy, and I'm very used to listen to people say I appear younger when I say my age, my dentist said the same thing. One day she asked if I have siblings and I said yes and I was the youngest, she said I "was the little baby in the family". A month later I cut my hair (I used to have a long hair), she said that I looked even more younger with "baby's face". The strange thing I am 5'9 (1,80 m) tall and weight 130 lbs (58 Kg). I don't feel comfortable if that, I wanted to appear more older but I still don't have a beard (and nowadays if you are a male and don't have a beard is considered a crime). I have to just accept that or say I dislike to call like that?