Period and pregnant

Ok really confused. Half and half say you can and you can't. I have heard and learned and asked many doctors and Gynos and all have said if You have a period. Your not pregnant. So they said u can have pink bleeding 1-2 days implanted bleeding I guess. And than nothing more. Any other bleeding is bad. You should not have a period while pregnant. That is the way for our body to tell us we are not pregnant. I don't believe people who say oh I did or my grandma did. Sorry bs. U can't have a period and be pregnant no way. Who else sees this.