Doppler anxiety

I’m 12+3 with my 3rd baby. I’ve been able to find the heartbeat since right before 10 weeks. I don’t do it everyday but these last few I have. Saturday I heard it but it was so quick cause she moved. So I tired last night twice and I couldn’t find it so I tired again tonight and still couldn’t. This is the first time since being able to hear it I haven’t been able to find her at all. I’m so anxious now. I have an appointment Friday but it feels like forever away😭