I need to know the possibility that i got pregnant while i was on my period ?

That does not happen: A woman cannot get her regular period and be pregnant at the same time. However, she can get pregnant a week or two after her regular period. If she has some spotting or light bleeding that doesn't look like her normal regular period, she can check a urine pregnancy test about 3 weeks after sex (3 weeks after when conception might have happened) to see if she is pregnant.

If it is your : period, no. If you ovulated and had implantation bleeding this could be lighter and sometimes confused with a period. A pregnancy test would become positive after implantation bleeding.