Can you get pregnant if....

Question from a very inexperienced and unknowledgable girl: I'm not sure exactly how to word this, but if you have sex 3 to 4 days before you start your next period, and you still have that period like normal, could you still be pregnant? I just didn't know if since my period came so quickly after having sex that the whole not-having-your-period-while-pregnant thing would kick in yet or if it would take it longer. Does this make sense??? Any advice would be greatly appreciated!