Periods While Pregnant?

My girlfriend is worried she's pregnant. She gave me a handjob then rubbed over her undies. she thinks some sperm was on her finger.anyway, she was a couple weeks late for the period after the HJ. but ever since then, she has had periods.They start off pretty heavy but last for around 3 days. she has no symptoms so i dont know why im so worried.but is it possible that she can be pregnant and have some heavy bleeding?