I'm 29, and I've been cycling since I was 13 years old, so I look shorter and smaller than my peers, I used to be made fun of in my school for that, but I never thought of it seriously. Now I realize that I just don't age faster than others, which is a good thing. I just feel bad for the people who didn't realize it. So don't feel bad about it, as long as you are able to carry on with your life.