Eish, 4 hari delay memang bikin panik kan! Kalau test dah negative tapi period still tak datang, bisa jadi hormonal imbalance, stress, or ada perubahan dalam routine, a few of my mum friends pun pernah experience ni, especially kalau ada changes macam diet, exercise, or emotional stress. Best you see your gynae or doctor to rule out anything else, sebab kadang-kadang cycle kita boleh berubah tiba-tiba without obvious reason. Jangan worry dulu, tapi better check dengan professional just to be sure!