I see some "sit" in your delivery. At about the 3 second mark of the clip your center of gravity drops. This causes your momentum to be on a more vertical plane instead of horizontal (toward home). This is common in a lot of pitchers that are told they open up too early.
This is an example of; we don't always see what we think we do.
Look at the clip of Mariano Rivera that is on one of the threads. If we put your clips and his next to each other we would see very different movements. When you sit down, he is projecting his front hip toward the plate. This will cause his shoulders to tilt back (throwing shoulder is lower than lead shoulder). This makes a "V" shape between his right oblique and right thigh. He is able to do this because he keeps the weight on the inside of his back foot and directs his knee toward the plate. You will notice that he rides his back leg toward release. This keeps his weight back and allows his back hip to rotate through release instead of pulling open. This is very easily confused with sitting unless you know what you're looking for.
As funny as it sounds, check out the link: http://www.brooksartprints.com/Fastball.jpg
It is a painting of a young pitcher, but shows all the points I just touched on. Weight on inside of foot, knee inside foot, projects the front hip, "V" shape between oblique and thigh, head and shoulders tilt back.
Good luck man!