[Form Check] Deadlift 350x5

H: 6"1 W: 182lbs (though maybe a few heavier in the first video) 1RM: Untested

[Deadlift 350x5](http://youtu.be/SBxklmRtIfU?t=40s)

This was two deadlift days ago, so last thursday I believe. The first rep has some hesitation but it looks like I kept my back properly arched and powered through. Second kind of the same, but the third I can definitely see my back rounding before I get the weight up. Four is more of the same. Five is just gross, but I really wanted it.

Next deadlift day (monday) I wanted to nail down my form before bumping up the weight, so I kept it at 350.

[Deadlift 350x2](http://youtu.be/cAGNzIQgxv4?t=44s)

Immediately sag my lower back and lift. Second rep was even worse, and I pulled or pinched something during it and decide to stop.

Come back and drop the weight to 315, but the pull is similar to the first one in the second video, and I can still feel that pain so I put it down after one rep.

So what am I doing wrong? I almost feel like I'm hesitating, you can see it in the second video a bit (I was working out late at night but in the first one it was early morning and I had consumed caffeine), is it as simple as that or is there something I'm not doing after my first rep (which historically is performed very well)?

Sorry for the wall of text but I appreciate any thoughts or comments. Thanks!