To all ye horsey folk =) ???

my pony milo is being a brat ..... i have a paddock and a really big field and i am trying to ride milo in the big field but when i get half way across the field he pulls on the bit and tries to turn around ... i fight with him and then he bucks which is really annoying! its like he is being lazy and doesn't want to work... i cant do circles, cantering,bending .......What should I do?????? (desperate voice) =)