bummed & confused 🤔😕

Rina

4 days late today & my periods are 28 days to the day... have had cramping on & off & sore nipples.. just tested and got a BFN.. I keep reading about all these women getting their BFP up to 5 days before their missed period.. do i just not have enough HCG yet..? I thought first response was supposed to be extremely sensitive.. should I just re-test in a week..?