Not likely. But you shouldn't take it ceasing as evidence of pregnancy or evidence that you did not become pregnant.
Here's the thing: pregnancy is rarely instantaneous. In other words, it often takes several days for conception to occur after a risk (which is why emergency contraception can work). So, a woman who has unprotected sex while on her period, if she ovulates very early in her cycle (and we can't know about you unless you've been charting), can become pregnant.
(Not to mention that unprotected sex during menses is particular unwise becue STI risks are even higher then.)
So, smartest route for handling this risk? If you're not up to date with your annual sexual healthcare and STI screenings, schedule them for a couple weeks from now. You can get them then (as should your partner), and if your next period is late at that point, you can aslo get a pregnancy test then.
And in the future? Use condoms when you have intercourse, no matter what time of the month it is.