Back injury - Squat Check

[marc717]

Injured my back a couple of months ago with thaiboxing, dropped weight on the squat which resulted in dropping BW. So as of yesterday I'm back on GOMAD

In the vid I'm squatting 203 LBS.

SET 1
http://www.youtube.com/watch?v=sZJSPa7kunc

SET 2
http://www.youtube.com/watch?v=XBJ0pGU81l4

SET 3
http://www.youtube.com/watch?v=kxdDw5vd4JI

They look fine to me, except that on some reps the depth is questionable and I see a little butt-wink (butt-wink nazi over here ).
The bench underneath my ass is because I tend to go deeper then necessary and not shoving my knees out which results in a gigantic butt-wink.

But somehow I can still feel my back hurt a little after the sets.
Am I still doing something wrong?