soft as a pillow

Every morning for the last few weeks I have woken up with a pain in my neck. I assumed it was my Invisalign braces that I wear (constant adjustments on my teeth) but I'm really starting to think it's the pillow I was using.
One night I decided to change pillows for an experiment and voila! no neck ache in the morning. I was using one of the tempur-pedic pillows that is comparable to a slab of beef thinking I was doing myself a favor...guess I was wrong.