First time mom scared. UPDATED

I went to the doctor today for a check up and he used to Doppler but, then told me he couldn't find a heart beat however the machine has been acting up since yesterday. Told me to go back tomorrow morning and he will use his own. When I got home I started bawling, I'm scared. I've only gained 4.lbs since being pregnant. He says it's okay for now. Any thoughts?? 
UPDATE:
So I went back this morning he used 3 different dopplers and still couldn't hear a heartbeat. I have an emergency ultrasound at 3:40 today 😭