In your setup, after you grab the bar and crouch down (i.e. right before you lift), pull your chest towards the bar while keeping your arms straight (think of it like shrugging your shoulder blades straight back, except your hands remain in one place).
Vid would be nice. You might not be getting your hips low enough. Practice straightening your lower back by placing your hands on your thighs while standing upright, then slowly push your hips back and bend your knees until your hands slide down to your knees WITHOUT bending your torso over at all.
Also, you won't deadlift heavy weights with a controlled drop. After lockout, I keep it touching my leg and lower it to my knees (weight is on my legs, not my back), then let it free fall from my knees to the ground (with my hands still wrapped around it).
Dunno how tall you are but I'm 6'3"