Sore throat, headache, fatigue, & malaise x3 wks. sore throat has lingered for 4-4.5 wks. no fevers. neg throat culture & mono test. causes?

Posibilities: My first thought would focus on the nasal airway. If you have allergies/irritants/sinus swelling that narrows the nasal airway your mouth breathing during sleep will cause a sore throat. This can be aggravated in an environment like a heated house, because low humidity adds to the problem. A humidifier and generous use of nasal saline may give you some relief.