Sore throat may be due to viral or bacterial infection. In viral illness there is associated fatigue, nausea, muscle cramps which are self limiting in nature. You have not described whether there is any reddish lesion at throat or enlarged tonsils. Gargle with hot water with salt may help in symptomatic relief. Tab azithromycin orally for five days helps in getting cured from streptococcal sore throat. A cough syrup also has a role depending upon the nature of it whether productive or not. Take high fluid in diet riched with fruits and vegetables to get relief from fatigue. If the cough is present for more than two months there is a chance of tuberculosis. Its recommended to do an urgent sputum test. A contact history of tb, associated fever and night sweat also suggest this diagnosis. Fatigue is also very common in this. A blood sugar level assessment is also necessary at your age as it may cause fatigue. Again if the low mood is persistent for more than 2monthes and also disturbing normal daily activities you may need to visit a doctor for proper counselling as there is a chance of depressive illness too.