Confused

I had my first ultrasound today. By the looks of the ultrasound im 6 weeks. There was a flickering of the babys heart. But my last period was july 1st so that would make me 8 weeks 2days. Im worried because my last pregnancy ended up beign a missed misscariage and the baby passed on 8 weeks 2 days(the day after our ultrasound). Ive had morning sickness for like 2 weeks meaning i would have been 4 weeks once it kicked in. Did anyones date change by 2 weeks and everything be fine?