If I had unprotected sex the day before I got my period can I be pregnant?

It's possible. Any time you have sex it's possible you can get pregnant.

While it is less likely, it is possible.

It is possible. I assume you got your period? You should wait to see if you miss your next one.

In the meantime you might want to explore contraceptives like the pill or condom if you want to prevent a accidental pregnancy