What is the possibility of getting pregnant whilst on your period?

Slim, but not impossible. Be carefull not very likely. your period starts on day 1 of your cycle. most women ovulate around the 14th day, and there is a period of about 48 hours during which an egg can be fertilized. however, it IS STILL POSSIBLE! so please continue to use protection no matter where you are in your cycle, there are no guaranteed "safe" times.