I had unprotected sex the day before my fertile period started. What are the chances I could be pregnant.

How do you know WHEN your fertile period actually is? Don't tell me you feel it (its impossible) or you got some worthless app... (which is as useless as a Fortune teller)

If you had a clue when that ACTUALLY was you wouldn't be asking if you could get pregnant, you would know its always possible to get pregnant.. even during your period..