Measuring small at 7.5 weeks.

My last period was March 10. I have PCOS so I’m not exactly sure when I ovulate. I am high risk so I have been getting ultrasounds since I found out I was pregnant. At my 5 week scan I had a perfect gestational sac. At 6 weeks, there was a baby but no heart beat could be found yet. Today at 7.5 weeks, they said the baby had not grown in over a week and there was no heartbeat so to prepare myself for the worst.

I’m holding on to a tiny piece of hope.. Is it possible that I’m not as far along as my last period says and it’s too early to detect a heartbeat anyway?

My husband and I both thought the baby looked bigger than it did last week but they said it hadn’t grown even though it had a much rounder end hump than last time.

I’m just trying to prepare myself for the worst while also not wanting to believe that this is the end.