When you say "hurt" is it a muscular hurt, or a god dam there is something out of place back there hurt? Also is it middle upper or middle lower back?
If its a muscular hurt or soreness, my first guess would be that your using too much wieght, and your back muscles have to compensate. (I know this is never what anyone wants to hear)
I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.