Hi mommies in the house I greet u all.make una help me calculate oo wh…

Hi mommies in the house I greet u all.make una help me calculate oo whether na me no calculate well or scan. I saw my period from 17 to 21 of November 2020 so I did scan today and scan show 15weeks but to my own calculation I'm not up to 15 weeks.make una help me calculate too oo..thanks..