how much to feed??

Shiara • Im an 18 year old FTM, engaged to the love of my life, the beautiful man who gave me my perfect little son 😍 15/18/16💙
Soo were going to be introducing the bottle to our little man in a week or two, but im wondering how much he should eat?? Hes 3 weeks old today so hell be 4 or 5 weeks then..
We used the bottle for the first time the other day (i had a horrible migraine and legit could not do it..) so i hand expressed 2.5 oz and he drank all of it. But he really slowed down at the end and kinda needed coaxing to finish it. But i feel like thats not enough..? Thoughts? TIA :)
BTW i mean strictly breastmilk. Ill be pumping so no formula at all, dont know if that makes a difference or not lol :)