Dr appoint update

So I had my first official prenatal appointment yesterday. I'm 9 1/2 weeks. I came from a fertility clinic so I've already had many ultrasounds. Yesterday I was able to hear the baby's heartbeat on the Doppler but she said I won't have another ultrasound till I'm 20 weeks! I have to wait another 10 weeks to see my baby! I'm considering getting a Doppler but I'm nervous about it what if I can't find the baby's heartbeat cuz I don't kno what I'm doing?