Memory foam may not give you the support you need. Up until a few years ago you could buy a sculptured pillow with one side higher than the other and a valley down the center longwise. I have a Tempurpedic mattress but I did not get their pillow. The Tempurpedic is really just 2-3 inches of memory foam over a stiffer foundation. Otherwise you'd sink to the floor.
Same thing happens with your head. Get some support. Something like this:
http://www.thepillowplace.com/contoursupport.html
Just make sure you get one that won't crush to nothing.
Oh, and I have that grinding noise in my jaw every since a bad bout with TMJ 2 years ago.