it could be the mattress itself the positioning of your body whilst sleeping or the material the pillows are made from. i would say to invest in another mattress or try sleeping somewhere else to see what happens. your neck is greatly affected by the positioning of your body.
why am i getting migraines in my sleep through my neck? . i am waking up in the night with terrible neck pain that leads to a migraine. i have changed pillows as well as the height but nothing works.