I'm not exactly sure what you are asking, but this should cover it:
1) You CAN get pregnant while you have your period
2) Some women experience bleeding (not normal) while they are pregnant which they mistaken for a "period".
if you're asking if you can have a period while pregnant....yes you can. it can be anything from light implantation bleeding to a full on period. no having a period isn't normal but having it doesn't necessarily mean anythings wrong. you'd just need to go to your ob and have him/her make sure everythings fine.
or if you're asking if you can get pregnant while on your period....it's rare but yes it can happen. there have been women who've gotten pregnant while on their periods.
It is not possible to have a "period" when pregnant - a "period" (or menses) refers to a very specific type of bleeding in which the uterine lining is shed when an egg is not fertilized.
http://www.thelaboroflove.com/articles/can-you-have-your-menstrual-period-while-pregnant/
Bleeding while pregnant is not normal but occurs in approximately 25% of women. About half of those go on to have a miscarriage ESPECIALLY if the bleeding is heavy, accompanied by clots, and cramping is involved.