Can a girl still be pregnant if she get her period ?

Not likely: No, if menstrual cycles are occuring normally, then it is not possible to be pregnant. However, it is not uncommon for women who are pregnant to have some slight bleeding/spotting during the first trimester.

Not technically: While bleeding with pregnancy is very common--probably as many as 40% of pregnancies are so affected--it is not menstrual (a period) in origin. Some other cause is to blame. You should always have any bleeding in pregnancy checked to rule out the scary causes.