I'm kind of insecure about being insecure

So I'm fifteen and I've been debating writing this but i guess I'm looking for other girls that maybe have a similar issue. Im fifteen and I don't look my age, I look like I'm 13. I spend lots of time looking at myself and I want to change a lot of things so I can look older but whenever I share my feelings about myself I get shot down by everyone saying its stupid to worry about how young you look. I'm sure it it is inconsiderate and stupid for me to talk about how I feel about my situation and it probably looks like I'm in need of some type of attention but I can assure you...nothing because I don't know what I need hence the posting of this. People treat me slightly differently because they think I'm younger or because I look young they assume I'm naive and small minded but other than me dwelling on how I look, I'm really otherwise a wiser fifteen than most. Idk maybe I'm in the wrong here what do you guys think?