How can you tell the difference in naseau due to period or pregnancy without a missed period

By having a period: A woman cannot get her normal regular period and be pregnant at the same time, regardless of nausea. But, she can get pregnant a week or two after her normal period. If she has some spotting or light bleeding that doesn't look like her normal regular period, she can check a urine pregnancy test about 3 weeks after sex (3 weeks after when conception might have happened) to see if she is pregnant.