8 week ultrasound issue

So, in April we had a miscarriage. Found out mid July we were pregnant. Today went in for my 8 week 3 day ultrasound (according to my nurture/Glow calculation). But we went in and I’m measuring 5-6 weeks. But they found a tiny heartbeat flutter a couple of times. And there was an “unknown circular object” near the yolk sac and what they said was baby. They didn’t give us a rate for the heartbeat, and didn’t want to give us pictures. I just don’t understand. I tracked all our things, so I’m pretty positive by 1-2 days when I ovulated. So I’m not sure how they get me 2 weeks later. They said don’t worry, and we are going back in 2 weeks for another ultrasound to see. I feel like I can’t get excited. Super confused how this even happens. And just stresses me out and worries me. I feel like the way they acted and didn’t give us much that I should plan for the worst now. Anyone had something similar? Any ideas?