Felling Insecure And Lacking Confidence?

Hey, I'm 16 years old and I'm very uncomfortable with my self esteem I lack confidence and I often compare myself to younger girls wishing they were my age and me feeling like I'm so much older than they are, I don't mean to sound like a pervert, I find encouragement through some things yet I always end up thinking the negative about myself and how I just sit and think all those younger girls do so much and I feel like I haven't have as much confidence or self esteem as they are, I'm meaning I could see a 12 year old and say, gosh I wish I was her age again, like I'm growing up so fast, developing faster and I just need some hope, Thank You For Your Suggestions, also I feel afraid to wear purses in public and big earring or even tight shirts because my figure isn't like any other of these girls =(