STOP TAKING FIORCET NOW!!!!! I can't speak from personal experience, however, my mother became extremely addicted to it about 7 yrs ago and it caused some major health problems. She had to undergo physical therapy as well as psychological therapy after a 2-yr addiction that no one knew about. (And she's like June Cleaver/Carol Brady, so it was a shock to everyone...) It's an extremely dangerous drug and must be avoided, especially since you are pregnant - I don't have a medical degree, but if it was that bad for a 60-yr-old, it can't be good for an expecting mom!!
There MUST be other options. If necessary, consult another OB for a 2nd opinion. I suffered pre-menstrual migraines when I wasn't expecting, but now that I am, I haven't had a single one. I would ask about other migraine meds like Immitrex or Amerge, but I'm really not sure if those are safe either.
Hang in there, but do not take one more Fiorcet pill!!!
(Having read the other responses, I imagine that if you take them VERY seldomly, you'll be OK. I'd get another opinion, though, and if you find yourself needing them on a daily basis, I'd find another drug...)