It could be SM, my dog Jack Sprat was diagnosed at 5 months. From the time we got him at 3 months he scratched a lot. At first we thought he had allegories (I even joked that he was OCD), and the mornings were always the most intense itching. He was also crying out for no reason on occasion and bunny hopped when on a lead wearing a collar. The only way to know for sure if the symptoms are mild is is an MRI and they can scan your dog at any age. Just to be safe, I would also get your dog a step-in-harness and get rid of the collar.
I hope it is not SM, it is heartbreaking to know your baby is in pain. Jack gets weekly acupuncture which has really helped him with the symptoms in addition to the medication.
Mary Ann (Jack Sprat's mom)