Neck pain is mainly a result for bad posture at work & at home. While we are awake and conscious we try to be in a 'normal' posture but when you sleep, you are not aware of the posture especially if you are using a big pillow. A big pillow will keep your neck in flexion and your trapezius muscles won't get enough rest and will be cramped all along till you get it treated.
As for your digestion problem... Have 1 tbsp cow ghee early morning with warm water and have small meals with high fibre content.
Next Steps
See a Physiotherapist and take pain relieving machines. Shortwave diathermy and ultrasonic therapy. First deal with the pain and then go for strengthening of the neck
Health Tips
Pay close attention to ergonomics when physio explains it