Hey mama, yes possible talaga na negative pa lang ang PT kahit 5 days delayed, lalo na kung short ang cycle mo like 27 days, kaya ang implantation ay pwedeng mas late pa. One of my mum friends had the same situation and she got a positive on day 7 ng delay, so hindi ka nag-iisa sa experience na ito! Best bet is to retest after a few more days or see your doctor na lang para ma-check properly and may peace of mind ka na, especially kung gusto mo talaga malaman ng sure. Fingers crossed for you, mama!