if my boobs aren't leaking does it still mean milk is in them ?🤔

Caitlyn • Mommy of 2 + 1 on the way
When is your milk suppose to come in (in your boobs) ... is there a certain amount of months or weeks you are when it comes? Or is it just certain women that it comes faster or later ? My boobs are super heavy and my nipple have white centers but milk hasn't leaked or anything ?