Assuming that her menstrual cycle is 28 days long, my girlfriend's period was due Friday. Sometimes her cycle is 29-30 days long. She got her period today which is 3 days after it was due and said that the flow was very light. We had sex on Tuesday, 3 days before her period was due and at least 7 days after her ovulation. The condom broke but I continued using the pull-out method. She has indeed been under some stress so that could be the cause of the delayed period. Is the light flowing period normal or could there be another possible explanation for it?

She could just be having an off month. Most women will experience an abnormal period at least once in their life.

But, having said that, the pull out method is not a form of birth control. Also, unless she knows for sure when she ovulated, you can't assume that you had sex when she wasn't ovulating. Women can even ovulate during their period. It happens more often then you would think.

In other words, if you had sex, even protected sex, pregnancy is possible.

Wait until her next period is due. If that one is off, or she skips it, then try a pregnancy test using first morning urine.

Fact is, if you continue to have sex, anytime you do, no matter what sort of protection you use, pregnancy is always a possibility.

Good luck.