Sir. Headache can be due to numerous reasons like migraine,unresolved sinus infection, allergies, inner ear infection or defect etc. Based on the history you have given, I am suspecting allergic reaction to dust mites. Switching on the fan inside a unclean room will recirculate the air inside room along with the dust particles settled in the room, so inhaling this dust filled air on regular basis can cause repeated sneezing,running nose, headaches. So mainly I suggest you to clean your room including the fan and if possible sleep with a window open in a clean room to have a fresh air. Daily morning do jogging for 30-40mins and brisk walking for 15-20mins. Do breathing excercise for 15-20mins and meditation to develop stamina. Get a allergy test done to know about the things you are allergic and avoid coming in contact with such things. If you are not satisfied kindly consult a physician for further management.