can u have a period and be pregnant

People on here seem to be all over the cam u be pregnant with a period. I highly doubt you can. I know you can have 1-2 days of light bleeding if your having implation bleeding. But u can't have a full fledge period and still be pregnant. U can read online you can but that doesn't make it true. Doctors have said don't go reading online because a lot of stupid stuff you will find. So what do others think.