Aihhh mama, nervous betul ye, tapi ni memang confusing situation. Honestly, dari apa korang describe, it does sound like possible vanishing twin or maybe slow-developing twin situation, the tiny dot yang muncul then disappear, then appear lagi with heartbeat, tu really tidak typical lah. A few of us dalam mum group pun pernah dengar pasal vanishing twins, tapi usually by week 9 dah clear lah one or two babies, bukan jadi tiga ultrasound, three different answers gitu.
Better check dengan doktor yang sama (obstetrin) untuk follow-up TVS scan after 2 minggu ye, because the abdominal scan tu tak dapat detect details kecik-kecik macam tiny dots tu. Doktor kena tengok sendiri dengan TVS, bukan depend on abdominal je. Jangan stress sangat dulu, majority cases macam ni turn out fine, either one healthy baby or genuine twins yang both okay. Just get that confirmation scan and let the obstetrin guide you from there, okay mama?