It is unlikely that you are pregnant. The pill works by stopping you from ovulating. You were clearly past the ovulation point when you messed up.
The EC stops the fertilized egg from implanting and it seems like it is unlikely that there was any egg around when you had sex.
If you are not on the pill, the chances of you getting pregnant during your period is minuscule. The possibility exists in theory but in practice you will have to menstruate and ovulate at the same time. That is a tremendously screwed up cycle and should be very very rare.
The problem is normally that women mistake bleeding for their periods and thus think that they are safe. As you are using the pill, this is unlikely.