Wa'alaikumasalam sis! Delay 3 hari dengan pening-pening dan sakit pinggang memang boleh jadi tanda awal, tapi ujian negative tu juga kena ambil serius, kadang hormones je yang berubah, especially kalau cycle kita memang irregular macam bulan lepas. A few of my mum friends pun pernah delay berkali-kali tapi ujian negative, akhirnya it was just stress or hormonal imbalance je. I think best you check with your gynae to make sure semua okay, pastu boleh dia advice kalau perlu cycle-tracking atau check hormone levels, don't worry, you're doing the right thing by being aware!