Its very possible and not to mention the STD"S in this country are very high. Maybe he is manogamous, maybe he isnt but there is no way I would play those kind of risky games in this day in time. You should know better. And being pregnant is something that could be a possibility too and are you ready for a child? Can you afford a child now? You should think about all of this before you do this kind of stuff. No being mean, just getting real!
It is very, very unlikely you would become pregnant five days before your period is due.
Hormone levels are not high enough to support egg fertilization the week your period is due.
A Period of Wellness, non profit about menstrual cramps, color of menstrual blood and such
http://www.vascular-events.com/fluid.aspx