Ok, so the song is pretty obvious, really. But for further analysis:
On VH1's Storytellers, John Mayer talked about some of the meanings behind some of his songs and why he does this, that, and the other. He played 'Your Body Is A Wonderland' in the program.
He talked about when he was 14--either he lost his viginity or this one just one instance--he was having sex with this girl and he wrote down how he was feeling at the time. He said he picked up his guitar and started messing around with it while he was still naked lol. But yeah, if you want more, just watch VH1 Storytellers: John Mayer. It's very interesting. Only I wasn't expecting him to be so open about his sex life lol totally took me by surprise.