The song is about that feeling of complete and utter desperation and devastation that comes with complete and utter rejection from an unrequited love, one that he's so totally enamored and obsessed with that he wants such an intimate but otherwise menial notion as tracking the moles and freckles on her back. He's realizing it's time to move on, so this becomes something of an confession of his transgression and an apology for the hassle it's caused her.
The song is about that feeling of complete and utter desperation and devastation that comes with complete and utter rejection from an unrequited love, one that he's so totally enamored and obsessed with that he wants such an intimate but otherwise menial notion as tracking the moles and freckles on her back. He's realizing it's time to move on, so this becomes something of an confession of his transgression and an apology for the hassle it's caused her.