Dear girls! Help! 8 months ago I had a missed miscarriage; it still we…

Dear girls! Help! 8 months ago I had a missed miscarriage; it still weighs on my mind and I'm very worried. I'm 3 days late, with 4 positive tests. When should I go for an ultrasound to confirm an intrauterine pregnancy? Last time I went at 4 weeks and 5 days; they said it was positioned awkwardly and to come back in 4 days to listen for a heartbeat, it was a very early gestational age. The next day I ended up in the ER, and a week later I had surgery — the embryo had stopped developing. For me it was such a tragedy; we treated everything in time and now this moment has come. I'm writing to you and crying. I'm afraid of a repeat, afraid of doing something wrong. Is it better to wait, maybe do serial hCG tests, or go straight to an ultrasound? Thank you in advance!