Can a woman be pregnant and still doing period n if she go for scan

Can a woman be pregnant and still doing period n if she go for scan, scan will show she is pregnant next month scan will show she not pregnant what can cause it

IT might Be pregnancy But when the mother try to abort it and it fail ,it become bleeding not period. And it will lead to miscarriage if the abortion is not reverse. And because of that the scanning will show baby which is actually there and also the woman may bleed thinking is menses which is not but rather bleeding that may lead to miscarriage ,due to fail chemical abortion .Thanks so in conclusion see a doctor