my B is almost 7-mth, she somtimes drinks 4oz a day, I got the same problem with you, but you just don't worry too much for now cos it's only the beginning, she/he will change the behaviour later on , you can try let her sleep more if she really doesn't drink.
I also need some opinion from mame (pls see the other topic "HELP! BB 嚴重厭奶, what can I do?“ cos I'm been suffering for months, THANKS