@Billie2, big hugs for you lovely.
It's not unusual to not even see the fetal pole until 6 weeks. And a few days can make all the difference.
You are still so early on, and under 'normal' circumstance most people don't even get a scan until they are past 6 weeks. Our radiology department here actually said to me "We wouldn't normally even do a 6 week scan as more often than not they aren't conclusive, and our ladies get upset even though it was just too soon. By 8 weeks we get a much clearer picture."
I know *most* IVF ladies will tell you they see a HB at 6 weeks but I promise you it is not unusual not to.
I think...prepare for the worst and hope for the best is a god plan. Hopefully you're just a tad early and all is still well