hey man,
Have you tried any stabilization exercises for your lower back such as the single leg deadlift? Hows your warmup you do any active stretching? Do you do any dynamic warmups for your back. This may help you out. Mike reinold of the boston redsox shows a postural exercise for you back. Its a lat pulldown with a little twist. Use the information if you want bro hope it helps
go to mikereinold dot com and type in lat pulldown in the keyword box on the top right of his website. it will show proper form. He also explains why he does the lat pulldown that way