Will I ever feel like an adult?

I'm 23 and I still feel like I'm 15. There's so much I don't know and although I have a somewhat normal "adult life", I feel like I don't fit in the adult world. I still feel like a teenager. Twenty three sounds so old and I don't want to get older, because I don't feel ready. I have no idea what I'm supposed to do and I wish I could be a kid again. Will I ever feel like an adult?