Could be nerve pain from a post herpetic virus, VZV or HSV-1. Those virsues tend to like hide in the occipital and trigeminal nerves. The post herpetic neuralgia is usually a burning type of pain. I know because I have been battling it for 4 months now.

Hve you docs run a IGM and IGG tests for the herpes zoster, Hsv-1 and vzv viruses. If the IGM is elevated then you have had a recent infection. And they do not always come with a rash or cold sore by the way.