Agreed with the above ^^ posts. Now, it could be the saddle, maybe it doesn't fit you right. If that's not the case, and even if it is, try to deepen your seat in the saddle. It kinda looks like to me you are trying to use your feet more to keep you in place, and it also looks like you are using them to brace the impact of the movement of the horse. You should be just ridding it out a little more (if that makes sense). If western is your kind of riding than you need to relax your body way more, because you look like you should be ridding english by the looks of your posture. Also, if your horse has a "go" button, meaning he is real responsive and likes to "go" with the touch of your leg, that could be why you are ridding the way you are. If that is the case, try to desensitize him to leg pressure a little bit. Other than that, I'm not sure what else to say lol. You do look like you know what your doing for the most part though so thats always a plus in my book haha.
