Hi there OP.
From what you have told us, I think you are saying that he is:-
- high spirited in the field and
- difficult for you to control on the ground, by which I mean he isn't really listening to you.
I also get the impression that his behaviour is making your nervous, or at the very least making you believe that you can't handle him?
Horses can change from 'calm and laid back' to 'spooky and hot' very easily. The reasons for change are many, but here are some likely ones:
- he is possibly getting more high energy food than he needs
- he is not getting enough discipline to keep him well-mannered
- he is bored, and needs both mental and physical exercise.
You say that you are working with a trainer, but I'm going to say that if your trainer really was helping you, these problems wouldn't exist. Either the trainer is no good, or you're not asking the trainer the right questions. Whichever it is, you're wasting your money if the trainer isn't helping
So: either find another trainer, OR sell the horse.
If this horse is too much for you to handle, then the best thing to do FOR THE HORSE is to sell him to someone who can work out these problems. Because the longer you have him without resolving the issues, then the harder it will be to find him a good home.