Heartbeat with a doppler at 18 weeks

Hello Ladies, last week I had my 18 weeks appointment. The doctor used a doppler to listen to the baby’s heart beat. It took her sometime to find it. She was scanning really low after few mins she said it is 138. So I asked her but I didn’t hear it. She showed me on the doppler the number and said still early to hear it. We check and see the number once she sees a high number that stays for a min or so means she found the baby’s heart beat. She also said do you hear the woshing sound, it is the baby moving that is why she could’t catch it easily becasue the baby was moving. Now I am worried because I haven’t felt the baby yet only feels flutters here and there. I have my anatomy scan next week.