One idea that comes to mind is that it is an inflammation pattern that ebbs and flows perhaps related to your activity level: it gets triggered, which either impacts your spinal cord, a nerve relevant to a gland over or under producing a hormone, or some other systemic mechanism. Perhaps you should try to modify the cycle by either decreased or increased activities. If, for example, on your most painful day, you were very active, I wonder if the pain would last into the next day. Or, if you did nothing for the better part of a week, perhaps the cycle wouldn't start.
Of course, I'm not an MD, but thought I would mention what came to mind.
C4-T4 Scoliosis (disk degeneration, stenosis, narrowed neuroforamen, bone spurs), RT hip and SI joint damage from car accident. Also, pectus excavatum, supraventricular tacycardia and mitral valve prolapse syndrome.
Current meds: Ultram ER 300mg daily, breakthrough - hydrocodone 10-15mg, or oxycodone 5-7.5mg. .25-.5mg ativan as needed for sleep, Verapamil 240mg SR (for tachycardia). [/gray