Baby measuring small and huge range in heart rate 🙁

My baby has been measuring right on time thus far in my pregnancy, and went in for my anatomy scan at 21 and a half weeks. At my appointment the few days before my babies heart rate had dropped so low they thought it might be mine on the Doppler and did a quick check via ultrasound, and it had gradually came up to top out at 120 exact. (Had previously been in low 150s high 140s) doctor just said they might have been sleeping and could be a boy.

Fast forward to my scan, babies heart rate is 147 and the baby is ten days behind now. They couldn’t get a good look at the heart either so Now I’m stuck for three or four weeks until they give me orders to come back in for a recheck on growth and to try to get the heart again. Baby is still moving but not as much (still ten kicks an hour minimum)

Has anyone else experienced this?