Do you ever adjust to the uncomfortable and achy feeling of your breast filling with milk?
no u dont lol my daughters four months on the forth and they filled up over night and i woke up with painful boobs ugh
it's most likely let down, I don't think you feel the milk come back in ( your breasts are never 100% empty either) does it happen around feeding time, when it's time and baby fusses? or right at the beginning of nursing?
it's your let down, not really your breasts filling up, I always feel it at those times and sometimes my breasts are already heavy and full