My3Girls, my DD lost 15% of her rather huge birthweight (apparently its more common in big babies, i seem to remember midwife saying) in three DAYS. I had no help from the hospital midwives at all and was sent home with a baby that wasnt feeding properly. She became jaundiced and dehydrated. I was lucky enough to be able to go to my local birthing centre where they were FANTASTIC, and my very strict german midwife (who was luuurvely!) was as determined as me that i was going to continue to BF, despite advice otherwise from my mother and MIL. I did have to put DD on formula for a few days, just to back up what i was giving to her, so i would breast feed and then give her some formula (it just got her over the initial slump). Then my milk came in AND HOW, i was getting DD ready for a feed and my DP, who was allowed to stay in birth centre with me (cant praise them enough) was laughing hysterically - my milk had come through, day 5 - in floods, it was literally pouring from me and pooling on the floor! I still had a few problems and i was advised to express my milk, i hired a contraption from the NCT, honestly i felt i was strapped to some sort of ancient torture rack, but i did this until i was able to BF completely. I was knackered, i was eitehr feeding or expressing. But in the end i managed to BF DD for 5 lovely months, i wanted to do more but i had gall stones and the fat free diet buggered my milk supply.
DONT GIVE UP is my message, you just keep feeding your DD and she will take what she needs. I did have to top up with formula in the end as my milk supply was affected by being ill and people told me i was mad to put myself through it (i discharged myself from hospital so i could go home to BF, doctors were horrified! but you know how it is with your baby, they come first).
I couldnt have done it without the support of my midwife though as i was convinced i had starved my poor wee bairn.
So my advice, FWIW, get a breast pump, if she feeds for a short time, express the rest of the milk and offer it later, or express some of the foremilk, not all, she needs it, and then offer her the breast.
GOOD luck with it and DONT give up. BUT, if it does get too much, dont beat yourself up, youve done your best and will continue to do your best for your little one. Go Girl