Could be a sign of vitamin b-12 deficiency, which will show up in standard blood tests because of overly large and immature red blood cells. However, vitamin B-12 is notoriously difficult to absorb, and just as a suggestion (provided you're actually b-12 deficient) you might want to try a separate sublingual b-12 supplement that contains at least 1,000 micrograms. You could ask the pharmacist in your local grocery store about this - which b-12 supplements are best in terms of absorption.

Like you said though - it could stem from any number of things, such as a kink in your neck that isn't being worked out or whatever.

Might wanna go see the doc to find out what is causing this.

Hope it goes away soon.