You need to get your hand off of the horse's neck! You have the reins choked up and your hands are all the way up on the horse's neck resting in place and never moving. Correct equitation calls for a straight line from elbow, hands, to bit. That way you have correct contact with the horse's mouth. It's better if your hands don't rest on the horse's neck and that your thumbs are up and turned SLIGHTLY inward, making an invisible X. Hands are especially important in eq classes and dressage. Having correct eq, however, leads to better rides even if its a hunter or jumper class.
I like your forward seat when you're jumping but try to sit deep and back when doing flat work and dressage. :)