Doppler causing panic 2nd pregnancy

So this is my second pregnancy and I’m 11W today. I still have a Doppler from my first pregnancy, I found the heartbeat at 9 weeks with my first pregnancy and found it really good between appointments and scans. This time around I tried from 9 weeks and cannot for the life of me find it, I know where to look because I used it a lot first pregnancy, I have looked EVERYWHERE high and low for at least 45 mins a day, since 9 weeks, I can hear the whooshing sound of the placenta and occasionally I’ll see the screen briefly flick to 130+ BPM but I can’t hear anything that remotely resembles the babies heartbeat that I know seeing as I used it with first pregnancy. I have a 12 week scan next Thursday but I can’t help but freak out - why did I find it so easily with my first pregnancy and

Not this? The only explanation I can think of is that my placenta is anterior, whereas my placenta was posterior. I’m still really sick with morning sickness so I feel pregnant but I can’t help but worry I’ve had a missed miscarriage and will find out at my 12 week scan 😞 anyone have experience with second pregnancies finding the Doppler heartbeat later?