Nobody ever expects you to be who you are. You don’t expect many other people to be who they are. A first impression is mighty, but it’s also not the whole story. I’ve noticed that nearly everyone you talk to starts with shallow expectations and ends the conversation surprised about who you turned out to be. That may or may not be a problem. What happens when you don’t have the chance to sit down with them and answer their questions for an extended time? They’ll leave thinking you’re what they thought you were. You’ll have failed to break the mold.
Of course, you can’t explain your entire being in an elevator pitch.* But I recommend you pay more attention to your first impression. This may come in the form of dressing well or being more deliberate in how you introduce yourself. Right now, you have leverage by stating your age. People are intrigued by that detail. Soon, this advantage will wither away, so maybe it’s time to pave other avenues. Don’t portray yourself as a child, and perhaps you won’t be viewed as one.
*Maybe you can—that’s what great storytelling is for.