I didn't have this as a symptom of PAWS, but about ten years ago I had a three-month stretch where I had almost daily migraines. X-rays, MRIs, nothing shows up, until one day I'm out shopping and pick up new pillows for my bed ... Solved the problem immediately -- overnight, you might say.
If your pillows are old, they won't provide proper support. If you haven't already done so, give this a try.