I actually feel both older and younger. Since I was 12 or something (I'm 19 now, by the way) I've always had the feeling that I was capable of making more mature decisions about stuff than others of my age (or even older). I'm also pretty sure that I've been seeing a lot of things in our society in a realistic way since I was very young (stuff like poverty, emotions, serious things in general). It might sound cold, but since I can remember I kind of realize that the world can be harsh and awful, while others (even of my age) just ignore or don't realize that.
In other aspects I feel younger. I can't really give you examples because I'm not sure about in what aspects I feel younger. Sometimes I sit in the train and spot someone of aprox. my age, and think: "Am I really as mature as him/her? I don't feel like I'm someone of that age".