Oh god, sleeping on a sunken bed is the worst! I feel ya...
Your neck problem could either be from a muscle or bone. Best bet, get to a massage therapist and let them know what's wrong. I always have neck/back pain because of mild scoliosis, and it's incredible how much better you can feel after a good massage.
If you keep having pain after a massage, it might be skeletal. You might want to see a chiropractor or your normal doctor and have an x-ray done to make sure you didn't dislodge a vertebra or something.
In the meantime, you need an even, flat surface to sleep on. It will help your spine & neck straighten back out. That might mean sleeping on a flat couch, in a sleeping bag on the floor, etc. It's best to have a thin pillow, or none at all, so you don't overextend your neck.