Ahhh banyak yang kena macam ni time dekat due date! Sakit yang datang pergi macam tu biasanya Braxton Hicks saja (practice contractions), especially kalau hilang lepas isyak, tapi since you're already 40w1d, memang baguslah monitor closely, and kalau sakit jadi stronger, lebih kerap, or ada discharge/spotting, better to call your clinic or hospital je untuk peace of mind, okay? One of my mum friends thought the same and turned out labour pun started few hours later, so never hurts to get checked, especially when you're this far along!