If your back is hurting from playing it is almost certain that you are hunching over the instrument, possibly trying to see the fret board. You should never hunch over the instrument, and you need to break yourself of trying to look at the fret board for reasons beyond saving your back.
An occasional glance at the fret board, especially if you have "slid" the left hand a long distance from one chord or note to the next, is tolerable but anything more will handicap your playing and makes it harder on your neck, back and left wrist.