Doese anyone know the cause of yawning and what can be done to it?

For several monthes, ive been yawning none stop everyday. I think i actually spend 更多 time yawning than breathing. Its starting to hurt, it's extremly irratating, especially since it starts up randomly, even if i'm walking in public. So i have to stop whatever i'm doing to take care of it. It's so tiring, i just require some form of assistance with limiting it, 或者 at least understanding it.