Your movement is slightly flawed. I see your momentum going backward a lot. You should learn to try and stay even plain as much as possible. Think of this as a defensive player on a football team, you should learn to pick a line and defend again this line. This means that you will need to 1) learn to hit with more balance and/or 2) learn to hit the ball earlier and in front of you. However should you start hitting the ball late agin and again, move that line back further.
By doing so, you'll have to force yourself to move forward as the ball falls short, but have the discipline to move back to the plain. It also adds A LOT of extra foot work and movement that will make you burn more calories.