If you have a a stuffy nose, clear drainage, and headache, either you've picked up a cold or your fall allergies have turned into one.
You probably don't want to run out to the doctor, so try some home remedies. Gargle with warm salt water or use a saline nasal spray. Drink water with lemon juice, add garlic to some honey and eat it before bed. Try inhaling steam and drink more than the eight glasses of water a day, already recommended.