Kelly Clarkson - Mr. Know It All Lyrics Meaning

I think it's about exactly what it's called. Mr. Know it all. Obviously there is a relationship, and the boyfriend acts like he knows everything about his girlfriend when in all reality, he knows nothing. She's basically saying, "you don't know me, you know what you wanted to know, my breast size." it may seem odd, but most guys don't really try and find out the true personality of a girl.