No heart beat at 6 weeks? :/

Okay ladies so I posted about how I was supposed to be 8 weeks, but when I got my first ultrasound the measurements were 5 weeks and 6 days. That would put me at conceiving March 27th, but I got a positive March 26th??? So like what?? (My last period was Feb 28th and ended March 6th ish) So it’s been 4 days since then and I went to a different hospital for a second opinion. The measurements were 6 weeks & 2 days which matches up perfect with how far along my last ultrasound showed (Still don’t understand how.) However there wasn’t any cardiac activity☹️ My HCG levels are 29,000 (Not sure if that’s good or bad either🤷🏻‍♀️) Can anyone explain if something like this happened to them and they weren’t able to get a heart beat either or a similar situation with a positive outcome? Anything would be helped. My last theory was that maybe the baby had stopped growing but it’s grown since then.