Lyric discussion by babysgotthebends 

Cover art for Turn Blue lyrics by Black Keys, The

I think urbane is right on some counts, and to continue with this:

"I gotta stay on track just like pops told me to do"

The singer is trying to focus on the other aspects of his life and involves his father in order to make themselves feel better about staying in the relationship. They have more important things to worry about than their relationship.

"I really don't think you know There could be hell below, below I really do hope you know There could be hell below, below"

seems to point towards someone trying to tell him the relationship is turning sour and other people can see it. Continuing on this way could lead to hell for the singer as the relationship enters a downward spiral of negative emotion.

My Interpretation