Best time to take TransV?

Gestational sac palang nakita nung Feb19 na nagpa-transV ako that time around 4weeks 2days na daw. I was advised to take TransV after 2-3weeks. Now estimated 6weeks and 6days na tummy ko. Makikita na kaya si baby with heartbeat? Or should I wait until 8weeks?#advicepls #1stimemom