I agree with everyone. It certainly sounds like you are experiencing rebound headaches, and you're in the horrible rebound headache cycle. Certainly see your doctor, and be honest about the amount of excedrin you are taking and how you are feeling. You may also consider keeping a "headache journal" until your appointment, where you log daily what you eat, the drugs you take, and how you feel (headaches, migraines, etc). This is a helpful tool for both you and your doctor. As someone else already stated, be prepared for the headaches to get worse when you start to go off the excedrin. There are natural remedies for headache/migraine relief you may want to try as you come off the excedrin (ice packs, relaxation techniques, deep breathing excercises, vitamins/supplements, accupressure, massage, accupuncture, etc). You may want to make an appointment with a neurologist who specializes in migraine/headache care and will have a better understanding of rebound headaches than a general practioner.
~Sarah