Tired of being adult-like. What can I do?

Just keep being yourself. I can relate because I've always been mature for my age too, and has felt like I missed out on being at the same level of my peers growing up. But at the same time, this is a good thing because not too many people your age has the maturity that you say you have, so in some ways it can be an advantage. Just don't try to be something you're not.