I have had a sore throat, stiff neck, headache and fatigue for several days. what could it possibly be?

Se below: Might just be a typical viral infection but anytime that it is accompanied by a stuff neck, you should see doctor because of possibility of meningitis. I would do this asap.

See below: May be common cold (viral), influenza (usually w/ fever & body aches), bacterial pharyngitis, sinus infection, or mononucleosis (ebstein-barr virus—usually extreme fatigue). Can try symptomatic treatment (nsaid for pain/fever/aches; fluids; rest) or see pcp for exam, possible tests, treatment.