well for sure you cannot be pregnant just yet as your fertility period or ovulation wouldn't have started and your period had stopped the day before so you would have to do the test like 5 days after but i'm sure you aren't pregnant but you can still try the test.
Hello,
If I understand you correctly, you were just on your period yesterday, and had sex today, the 30th? I don't think it's likely you are pregnant. The blood on your underwear is most likely left over bleeding from your period yesterday. You could take a hpt just to be sure and to ease your mind. Good luck :)