Was told i had a miscarriage bc they didnt see baby on ultrasound

Hannah
I was told Friday that I was pregnant positive blood test. So Tuesday I go to the hospital bc I was cramping BBAD!! And they did an ultrasound and they said they did not see any babies and was quick to just write off as a miscarriage.. When your only a couple of weeks pregnant they can't see the baby yet, right? I need any advice I can get please!!