If you get regular 28-30 day cycles, it is unlikely that you have conceived in this cycle as your ovulation date would fall around 12-14 January, which was missed. You had intercourse during the safe period. Stress
seems to be the causative factor for the delay in your cycle. You should consult your doctor for further evaluation through assessment of blood, sonogram and a general examination if you do not get your period in another week. Take care.