My 10 yr old gelding is all of a sudden not wanting to do ANYTHING! I get him all saddled and tacked up.. get on him.. he walks about 10 feet and then he just stops and backs, so then I turn him around and he walks about 10 feet the other way.. then stops and backs! Tosses his head.. and acts like he is going to dump me. He did one time.. I keep pushing and pushing and he flipped his head and off I went. He is an easy 16.2.. and full of muscle. Any advice would be GREAT!!!!