Typical anxiety!! Not to be insensitive but I laughed when I first read your post because I have SO had thoughts like that. I can laugh at them now but when you're going throughout this, it's no laughing matter. It's just your minds way of not focusing on really stresses in your life, it's much easier for your brain to think "I can't feel my neck." I promise you, one day, you too will look back on this and have a good laugh. The fatigue is from being so anxious, it's certainly exhausting to be in that heightened state throughout most of the day.