I had an appointment where the doctor couldn't find the heartbeat on a doppler because the baby was moving too much but found the placental flow. She said that the placental flow is driven by baby. If you don't have a baby with a heart beat, you don't have a placental flow. I think your baby is fine which is probably why your GP was unconcerned.

Glad to see that you got to hear your baby's heartbeat this morning! Enjoy taking the tags off your maternity jeans