It sounds like the horse, himself, needs a refresher course in manners...a horse SHOULD NOT walk off on his own, just because your butt hits the saddle, and once moving he needs to stay in the gait of YOUR choice, not go faster on his own. Gaited or not, the horse's behavior needs to be 'reined in'... As a trainer, it always gets to me, seeing horses just waltz off just because their riders are 'up'...big pet peeve in training for me...horse needs to stand stock still until I give him a cue to go foward, sideways, left, right, whatever...
My recommendation is to find a trainer who will work simultaneously with the horse (to get his manners back in check), and you...maybe see if trainer has a lesson horse you could ride for a while, then start riding yours once you gain your balance and seat, and confidence back.
ETA, I just noticed that the horse may have been ridden in a different bit and you tried switching him over to a snaffle. Chances are the horse doesn't understand the new cues, and if you are new to horses, you probably do not have the skill needed to retrain him TO understand the new gear. I would go back to what he is used to, and if you are set on getting him in a milder bit, have a trainer work with him, so you aren't constantly blasting what confidence you have left, into the ground because you and the horse don't understand each other.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."
Last edited by mom2pride; 10-27-2010 at 11:31 PM.