Fiona is such a pretty name! Congratulations on your little sweetie. Sorry she has such difficult beginning in life. I'm sure it must be very hard on you.
I pumped exclusively for all of my babies for a variety of reasons (poor latch, flat nipples, reflux, feeding aversion, etc), so I know how very, very hard it is. I would not suggest pumping any less than 8 times per day. I pumped 10 -12 times per day which was of course a complete nightmare as I was caring for first one newborn, then a newborn and toddler and finally a newborn, toddler and 3 year old by the time I did it for the last time. There's just no easy way to pump and feed but here are some tips I learned to help keep your supply up:
1. Pump in the wee hours of the morning when supply is highest. (4-6 am is when I always got my biggest yield).
2. Cluster pump. This means you pump or feed every hour for once or twice a day for two or three hours. I used to pump at 4 am, 6 am, 7am and 8am. This cluster feeding tells your body that the baby is not getting enough and then your body will respond by producing more milk. It sounds awful, and it is, BUT you don't have to do it forever. Once my supply got the boost I needed I'd drop one, then two or more of those pumping sessions and go back to my regular schedule and my supply usually would stay up.
3. Try to pump for an additional 2-5 minutes after your flow stops. Often times you will tap into a reserve supply that you didn't know you had, and this extra pumping also tells the body that the baby is not getting enough and your body will begin to produce more.
The lack of sleep is tough, but remember at some point your baby will sleep for 4-5 hours at night, and eventually more, so you will get some sleep soon. I used to stop pumping at 11 pm and sleep like a rock until 4 am and that was heaven, but that didn't occur until 6 weeks or so.
I never took dopermine so I can't comment on that. Good luck. I know how hard the pumping is.