
Poor boy. Head held low can be a sign of back pain. If he were mine I would be taking him to the Vet and getting him checked over. The fact that he has already had one ruptured disc, makes me very suspicious that the next disc could becoming unstable. If that is the case, he should be under very strict cage rest, with absolutely no jumping or running.
My girl made a full recovery after her first ruptured disc, but then had further problems later on in life. It was very important to pick up the early signs (low head carriage, change in gait, proprioceptive deficit (knuckling under, standing back foot on piece of paper and slowly sliding it to the side, etc). When she displayed any of these symptoms, it was a case of cage rest, anti inflammatories, then gradually returning her to excercise. With careful management we managed to prevent any further severe episodes, but over time a number of her vertebrae fused together.