Supposed to be on period but blood stopped

Okay, im a virgin and my bf and i do everything but penetration.

About 2/3 weeks ago my boyfriend and i were fooling around, he may have gotten cum on the top of my vagina. I know the chances are slim and im not even sure that happened..

3 days ago he fingered me on the day i was supposed to get my period, but i hadnt yet. But after he fingered me and i started to bleed after.. i thought i had just started my period so i went to the bathroom and i wasnt bleeding anymore..and havent bled again once 3 days later.

If he just cut me (which i didnt feel), why is my period late???