At the first few weeks, it's very easy to tell if bb is hungry.
He would cry and open his mouth, move his tongue, shake his head with mouth open, lots of obvious indications..
But as he grows, he cries for more things than just hunger... e.g. for hug, for ppl to talk with, or just boredom
I can tell he's ok with 4-hour time lapse because most of the times during the day, he can sleep for 3.5 hour until he starts to make noise.
I can tell he's really hungry when i can't stop him from crying by hugging, talking to him, walking around, giving him water or soother
Water and soother are good indicators.
If he sucks with much strength, but stops and cries (refusing the water/ soother), it means he's hungry.
In any case, just try try lor...
We feel hungry sometimes too. You know how it feels, it's not that bad and bb won't suffer too much.
Crying is just their expression.
Feed him when you think he's very hungry and cries too seriously. Otherwise not a big problem if he's hungry for 15 -30 min geh. :)