how do I com off fioricet? Do I stop at once or decrease daily?

You are right for wanting to come off Fioricet. It has 2 components that cause trouble: butalbital, which can cause dependence and acetominophen, which can cause rebound headaches (or Medication Overuse Headaches MOH). If you stop this medication cold turkey, you could experience withdrawl symptoms from the butalbital and a MOH. I suggest you consult a doctor as to how to decrease your dose. I would not stop all at once.

I see that amigraineur has already posted the same response I would have.  Please don't try to wean yourself off this serious medication without your doctor's help.  Kudos to you for paying attention to your body's cues.  Luckily there are many other preventive medications (and lifestyle changes) that can perhaps help you with your pain.  Good luck, and let us know how it goes!