When to find heartbeat at 15 weeks

Abbs

I’m currently 15 weeks pregnant and trying to find my baby’s heartbeat with a Doppler. I’m getting a little nervous because I haven’t been able to find it and my first and only appointment was at 9 weeks to confirm. I haven’t had any bleeding but my family is military so we have to be seen on a post and we just moved so I won’t have an appointment for at least three more weeks.