Possible Pregnancy: What to Do When Periods Are Irregular

Question
My age is 19 no children my girlfreind and I just broke up and she is having a lot of stress lately and we had sex like about 3 weeks ago and now she is saying that she is 4 days late on her period she took a test and it said she was negative and she is going to take another one this sunday I was wondering what you would have to say is it more than likely stress or could she be pregant  

Answer
It all depends on when your girlfriend's last period started and when, exactly, you had sex. If she has a normal 28 day cycle (from the first day of her period until the first day of her next period) ovulation occurs on cycle day #14. She can only become pregnant if she has unprotected sex on cycle day #13,14,15, or 16. If she does become pregnant on one of those days, a pregnancy test will not show a positive result until 14-21 days later. The best time to take a pregnancy test is seven days after she misses her next period. If it is negative at that time, she is not pregnant. Stress can also delay a period from time to time, so she should take a pregnancy test, again, in another 3 days.Then you both will know for sure.