What Causes Light Menstrual Bleeding?

Hello doctor, me and my fiancé were enjoying our intimate moment one evening.there was no vaginal intercourse.he jus fingered my vagina and had cum on my belly.he also rubbed his penis against my organ but there was no penetration.but we were worried about the preejaculatory fluid jus by any chance during fingering if some fluid entered in.to be on the safe side I took idoz 72 between first and second hour of this. All this happened on 19th March 8pm after 9days of my previous cycle.I had my previous periods on 11th March 7am.my usual cycle starts on every 28th day.i had slight bleeding for an hour on april 11th which just looked like my regular flow in colour and consistency.but I didn t had my regular three day flow till now.what does this mean.am I safe?plz help me out.