I've had that sensation for years, ever since my fibro was diagnosed. Mine also began between my shoulder blades but eventually spread to my arms and legs. What is helping me cope with it now is using organic sesame oil, it's a massage oil not the cooking oil. It helps me deal with the constant itch.
Fibromyalgia, CFS, MCS, scoleosis, herniated disks, spinal stenosis, osteoarthritis, sjorgens, sleep apnea, asthma, allergies, headaches. On a regiment of different supplements including sleep supplements. I eat nutritiously and do not eat foods I'm sensitive to and ever since a back injury triggered my fibromyalgia, I have been doing prescribed stretches twice daily.