I had trouble at first once the dr found it on hers I knew where to look for it now I find it every time
I'm 19 weeks and I still can't hear mine. I am only able to pick up my own!
I have an anterior placenta too and it took my doctor, who is very experienced, about 10 minutes to find the heartbeat at 16 weeks via doppler (his resident had actually given up about 11 weeks and sent me for an ultrasound). My anterior placenta was confirmed the next week. At my next appointment, he found it quickly but mostly since I had just had my ultrasound that showed him breech so his heart was up above the placenta.
My midwife couldn't pick my son's heartbeat up till I was 17 weeks. We could hear movement but his heartbeat was kind of hidden by mine. It was nerve wrecking at times but everything was fine. It isn't uncommon and with your anatomy ...just give it some time.
Go right by your hair line and push down harder.
As the reasons u stated is probably why.& at this stage ur little peanut has lots of room to hide behind ur pubic bone. Do don't worry:)