Symptoms of a sore backed horse

Horse is hard to catch
When I brush him, he drops in his back.
When I go to saddle him, he drops in his back or he gets "antsy" and moves back and forth.
While girthing, pins his ears and possibly tries to bite me
When I first get on my horse, he walks away very quickly and rapidly
While riding his head is always way in the air.
While transitioning up and down the horse gets hard in my hands
Doesn't bend as easily to one side as the other.
Doesn't go down slopes easily
While jumping he refuses more jumps the longer in competition
While in small circles, changes canter leads in the hind legs
Disposition changes for the worse