there's a big question. wihtout a vid it's hard to know. a couplle random thoughts and I'm sure others will pile on.
- bad pain in the back often means lyou're losing the arch, especially if it's mid back.
- if you can locate a good vid showing RDL's i'd do that, RDL's really teach you to get a lot out of your hamstrings
- push your ass further back at the start and squat into it, really load your posterior chain at the start, like your pulling a bowstring and your hips are the pick.
- ass and shoulders come up at the same time.
- your back should get taxed but not brutally so.
- I think of arching the upper back, this takes care of the lower at the same time.
- Do GHR's
- Do touch and go DL. see if that helps.