This can be due to the emergency contraceptive
which you have taken.
The emergency contraceptive have hormones which make the uterus
unfavourable for the implantation
if there is some chance of fetilized egg is there. This hormonal
mauplation of the uterus some time present as discharge which can be very little in amount and sometime can be more.
There is very very rare chance of being preganant if you have taken the pillls within 72 hours and be sure this is not due to pegancy.
Thanks and take care