Hi, as per your history you had sex in safe period. This bleeding can be an abnormal start of your period or it can be a sign of early pregnancy
or, if not because of these two, it can be contact bleeding because of some pathology or infection in cervix
. If you dont want pregnancy, then you must go for emergency contraception
immediately.Although time to take Plan B
pill is 72 hrs after having unprotected sex but its efficacy decreases as the time interval inceases. So, in my opinion, you should take one as early as possible.