Brief Answer:
There is almost very low chance.
Detailed Answer:
Hello dear,
Thanks for trusting hcm about your health care.
I have gone through your history and understand your concerns.
As this is your third day of period and I believe you are still menstruating the chances of pregnancy are very very low but yes,there is nothing 100% because if your ovulation occurs early it may cause pregnancy.
Hope found useful, feel free to ask more information.
Good luck.
Regards