i look young for my age too. I'm really good at figuring out makeover type stuff so if you want- msg me with your email and send me a picture of you! I can't tell if I don't know what you look like now but I have plenty of tricks up my sleeve if you want good advice!
While I'm not a girl, my best advice would be to change your hairstyle. I used to have much longer hair and for the past year or so I have kept it very short, almost shaved. With the shorter hair I have noticed people treat as though I am much older.