Just wondering if there are any mums out there ...

Just wondering if there are any mums out there that can tall me how much to give my two week old? She is not latching on properly and when she does - using a nipple sheild she sucks it out to fast and ends up throwing it up and is very unsettled afterwards or she spits it out the corner of her mouth - soaking mum with breast milk. So I have resorted to expressing and then bottle feeding (as I am able to produce a huge amount - my freezer is full allready). I am currently giving her 100mls per feed but am unsure whether or not this is the right amount. Nobody has been able to tell me so far and my early childhood centre wont come and see me for another two weeks and I cant get a hold of them, and on leaving the hospital all they said to me was to make sure I expressed 800mls a day. I would love to hear from other mums who have had similar probs and have an idea of how much to feed.