Yes it is very possible. All women are different
It's probably your mind playing tricks. You wouldn't have any pregnancy symptoms so soon. It is possible to get pregnant on the last day of your period, though, if you are an early ovulator as sperm can live inside you for 3-5 days.
If you're worried about the possibility and it has not yet been 72 hours since the incident, you can take Plan B to avoid conception. Of course, it is always most affective the sooner it's taken. It can mess with your cycle a little, too, but it depends on the woman. It didn't mess with mine, but some women will notice an earlier/slightly later period that month, spotting, etc.