Im confused

So I'm babysitting my nephew and according to my sister he takes 6 oz every 21/2 - 3 hrs but I feel like its not enough 😱 he is close to 3 months old he cries ALOT I get frustrated ... Ive changed him rocked him did pretty much everything he won't even take a pacifier ... All he wants is to eat he doesn't nap long at all before he wakes up crying ... I may sound stupid but I just need advice because I can't do anything during the day cuz all he does is cry she has never mentioned stomache issues I know to ask all that because I worked at a daycare I'm lost with the feeding part ...