Measuring a week early - no fetal pole (HELP!)

So last Thursday on 10/10 I was 5 weeks and 2 days. I started spotting brown discharge and called my doctor. They told me to go to the ER to be checked because they were closing. At the ER they took blood and did an ultrasound. My HCG was 12,800. The ultrasound measured the gestational sac at 5 weeks and 2 days. Perfect. There was no yolk sac yet, but the tech assured me this was normal and I probably wouldn’t be able to see it til 5 weeks and 5 days. They also saw that I had a cyst rupture on my left side which was causing the spotting. The doctor told me everything looked perfect and to follow up with my doctor within the next couple days.

So on Monday 10/14 I went to my doctor and did an ultrasound and blood work. I would have been 5 weeks and 6 days. We could see the gestational sac and yolk sac was there this time, but no fetal pole. The tech measured the gestational sac as 6 weeks and 5 days. Almost a whole week ahead. They told me to come back in a week and if there’s no fetal pole or heart beat then something is wrong. At 5 weeks and 6 days I would think everything looks perfect. But the measuring a week ahead is what is concerning. Anyone know why that could be? Is there any way my gestational sac grew a whole weeks worth over 4 days since I went to the ER? I am terrified at this point. Someone HELP