Our due dates are oftentimes just an estimate (hence called estimated date of delivery or EDD) . So that means they can get miscalculated, too. It could be that it's not yet the time for the baby to be born on your expected due date. Other factors could be first-time pregnancy (primiparity increases chance of post term delivery [39-42 weeks]), obesity, placental abnormalities, and a lot more.
nabasa ko lang po😊