I think you may have just rushed a little bit. Down at the bottom, remember to get your shoulders behind the bar, and to engage your lats. For the lats, I like the cue "bend the bar around your legs."
Getting your shoulders behind the bar will drop your hips like half an inch, then getting the lats tight will raise your chest up like half an inch.
This subtle change will make your back flatter, and let you get your hips closer to the bar.
I think you just hunkered over instead of pulling yourself to the bar during your set up.