Okay so my horse is 16.3 hands and he jumps 80 easily,but today when I was riding him every time after a jump he would throw his head and shake it, I thought it might be me banging on his back but even when I stayed in light seat he did it. The last time when I rode him he only does it right at the end of our workout so I figured it just means that he's tired of working. I have thought that it might be his saddle so if he does it again I will see if I can get it checked out but for now I wonder if anyone else has an idea?
he's probably either in pain, off balance, or excited, Im assuming
For sure get him a check up, make sure the saddle fits, check for sore spots, and check his teeth. And then address your riding. If you are unknowingly messing him up by slamming to hard in the saddle, puling to hard on the reins when you land, not giving a proper release, hesitating, not in a proper two point, and basically just pointing and shooting, he will tell you something is wrong, by either bucking at the landing, or tossing his head. Also, is he fairly green to jumping? He may simply need more practise to feel comfortable. Last of all, he may just be excited after the jump. If you have ruled out everything else, and he is just excitable, I would work with grids, lots
of them, to get him realizing that even though he landed a jump he can't lose his head, that he needs to concentrate more more more.