Lyric discussion by mytreacherousfriends 

It's about a man who was with a prostitute (who was either a close friend, or he fell in love with her) and is writing about his concerns for her... That, or something bad happened to her, and he's writing about how he regrets what happened ("your lower back haunts me every time I come", implying that he could have helped her out some how) "If they treat you rough in the evening, You'll be alright by the morning Why would you do this if it's so goddamned demeaning?" < She gets with a lot of men who beat her up/mistreat her, but possibly it's the only thing she can do? Either way, his feelings towards her (either physically or emotionally) are preventing him from moving on or from helping her out.