Ledd: Why don't you explain what you do on back workouts, as how many time a week, sets & reps? And does this feeling just happen after back workouts? Are you doing too much cardio, too many times a week? Are you on one of those reduced calories diets or are you stuffing yourself with enought quality protein & carbs to recover & grow? In some extreme cases, a little blood work might give a hint to a chemical imbalance with-in the body.
Way too many guy's complain about a problem training on this board but fail to tell the whole story of their workouts, etc and than they expect positive suggestions. Might want to give people here some help so they might help you. Good Luck.