Sis, stress lang talaga madalas ang culprit, a few of us sa group namin delayed din by a week or two dahil sa anxiety and lack of sleep, then suddenly mag-period na! Two days is still very early for a PT to show positive anyway, kaya siguro just wait a few more days and try again, or better yet check na with your OB para ma-rule out kung may iba pang nangyayari. Fingers crossed for you, mamsh!