Hi I'm a 17 year old power lifter I've been lifting about 1.5 years my deadlift (with a hex bar) is about 405. I'm 6'4" almost 6'5" and my legs make up 60% my height. And my problem is that I have a lot of joint pain and when I go down to do the dead lift my lower back is straight but my shoulders curve. When I do this my back has no pain though. My question is, how do I help get my ass down lower and increase hamstring flexibility?