It will depend on how long you took before you had sex. if you are always having regular menstruation
and ideally a 28 days cycle, then after your last menses, you could engage sex 5 days after the last drop of blood without fear of any risk. To me, the period you talk about is simply as a result of side effect from the pill you took. As most of them always present with skipping of period or abnormal vaginal bleeding
. You should presently just allow some time and wait for the period when you normally had to menstruation then give it some few more days before you start thinking of pregnancy
Hope this helps you.