Hello,
Thank you for your question and welcome to Health Care Magic. I understand your concern.
All the details you describe indicate very low possibility, almost zero, that your girlfriend have a possible
pregnancy.
First of all, pregnancy occurs only during ovulation period, which depends on your girlfriends menstrual cycle duration, and the 3rd day after the periods is not included in the
fertility window.
The second important fact is that in order your girlfriend to get pregnant, you have to ejaculate inside, so the sperm cells could travel in the genital routes of your girlfriend, in order to meet the egg.
The third and the most important fact, is that your girlfriend is on birth- control pills.
With the above mentioned facts,I would like to calm you down because you have nothing to worry about.
Hope I helped with my answer. Feel free to ask again.
Kind Regards,
Dr. Ina