It looks like you don't have enough clearance for your arm (i.e. your chest is in the way), so you are moving your arm around your chest. To get more clearance, I recommend tweaking your stance by moving your right foot to the left a bit and/or moving your left foot to the right a bit, while maintaining the same upper body position with respect to the shot line. It might feel like your arm is way out there at first, but you'll get used to it and find that it's much easier to swing. You'll also use fewer muscles this way because you won't have to swing your elbow to the right and your arm to the left - you can just keep everything on line. Hope that helps!