I just did a quick search. Has anyone suggested occipital neuralgia?
There is a section here on NT on this.

Apparently it is often accompanied by derealization (surroundings appear "unreal,") and depersonalization (ditto for "self"). Seems to be located in the occipital/temporal region of the brain.

Lots on the web....at least you will see you're not alone with these symptoms, and at best you will find a physician to recognize and treat this. You might want to consider shopping for a new doctor, for I'm surprised this was not considered.

Best of luck...it sounds very scary, but treatable.

---Sylvie