My horse is a 5 year old and I have been having problems getting him to keep his head down on the bit, and it is only with trotting. When trotting to the left, with suppling he will usually bend and keep his head down. To the right, he is constantly tossing his head up and will not go down on the bit with an even hard amount of suppling. I started him in a snaffle bit, and he would pull my hands apart at the canter. I had a segunda bit on, and he absolutely hated it. I have him in a Dr. Bristol now, which keeps me in control without throwing his head all of the time. He has great feet, and his teeth have just been floated. He just will not bend to the right and will not put his head down. Any advice?