AvatarNathan Richer

i suspected it was some kind of posterior chain activity that set it off. i’m not sure how your DL form looks, but it is possible you have glute inhibition on the right side. if you do, then hip hinging activities will cause you to overwork the hamstrings and low back when the glute is not firing properly. in this case, your low back is firing up to compensate for lack of glute activation.

this is not a complete diagnosis – it could be a spine/disc problem that is causing back pain as well. i would get it looked at by a competent chiro/PT to make sure it is not spinal or a disc.  
then i would wait until the pain calms down. i have found Supernova work on the low back to be pretty good for this.
then i would look at breathing and make sure you diaphragmatically breathing. this will help you brace the spine properly which is your next project.  then if you have those two going well, i would get back into DLs not in WODs but more with traditional strength training to groove proper movement and glute activation.  for the glutes, i would focus on squeezing them like hell at the top of each DL.  there are other great glute activation exercises too: glute bridges, single leg DLs, etc.
if you find that you can’t squeeze your glutes for some reason, it is likely some other problem in your hip flexors which are causing the inhibition problem. Smashing the psoas (gut smash) and rectus femoris (use a roller or supernova), and then couch stretching every day, should help with that.
but make sure it is not a disc problem or else none of this will work and you may end up with a bigger problem down the line.