I have been having lots of trouble with my geldings lope. His trot is completely fine- he easily picks up a level headset (even free longing he carries his head correctly and trots slow with good cadence). However, when I ask him to lope, he falls out of the lope, counter canters, and on a longe line has an awkward headset. I can keep him out of the counter canter if he moves really fast. He also lopes really fast and uncomfortably under saddle. His lope does seem to calm down a little bit when he's going in a straight line for a period of time, but at any turn or corner he falls apart. His saddle should be fitting properly as I have been working with a saddle fitter. The whole ordeal looks very awkward.
My question is- how do I determine whether he has some sort of pain that is causing him problems at the lope, or if he's falling out of his gait because he's lazy and just needs conditioning and work at collection?
I have thick skin. If this is a rider error don't hesitate to call me out on it!