Angel,

From the straight on angle it is hard to see what is going on.

Can you shoot 45 degrees to the side?
I do see two things:

1. You need to sit on the box for a little longer
2. Knees are caving. This is usually a rooting issue. Try and root your feet as hard as possible and keep the weight on all three points of the foot. (big toe, pinky toe, heel)