I've been extremely exhausted for weeks. My back and my neck will not relax. I am constantly nauseous.?

Pls see your doc. It's impossible to say what you have without asking more questions and examining you but what you have is not normal and need to be evaluated by your physician. Hopefully it's something benign like stress, or mild infection and not something more serious. Please see your primary care physician to start and proceed from there. Good luck!