Pregnancy help please

Hello I went to the er due to bleeding they did a ultrasound saying i was 6 weeks one day they said they saw everything but the heart beat.8 days ago I had an ultrasound done at ob and they put me at 6 weeks 4 days saw gestational sac and yolk sac that was it.i don't understand how I got 2 different weeks.?has anyone had this happen to them what was the outcome?