Best and surest way is to ask your OB po pagbalik nyo sa kanila. You can also compare your bump if you have bump pics na side view. Usually visible naman na bumaba na. If you had difficulty in breathing weeks earlier and ngayon parang masmaluwag ka nang nakakahinga, that could also be a sign na bumaba na sya. However, this may also mean masmadalas ka nang umihi and you may feel some pelvic pressure, both are because of your baby's weight pushing on your bladder and pelvic region.
usually minemeasure po yan during prenatal check up