i know this is my 3rd but please help

how can i tell if Bubs has dropped into place???

with my first at around 37-38weeks? i felt a grinding pain and i noticed later my belly was slightly lower
but i dont remember it happening wit my daughter

right now ive got more pressure on my hips, pelvis, groin and bladder and feeling with my hands he feels low but im not sure if im feeling right or if his just sitting low cause his my 3rd???
if he has dropped do babies move back up or do they tend to stay low
and sitting so low this early could it mean he will born earlier or makes no difference??