Worried

I had my last check up nung may 4 and ok namn si baby narinig ko heartbeat nya through doppler.Then, yesterday nagpa check up uli ako pero d marinig ung heartbeat so i was adviced to do an ultrasound.Sa ultrasound same pa dn wla tlg heartbeat si baby.I'm already 4months pregnant at sabi ng OB ko dapt mabilis na madetect heartbeat ni baby.I'm very worried and stressed d ko maiwasan na mag isip but i'm sure my baby is ok..I will have my 2nd opinion today and hopefully my heartbeat na xa..Please help me pray for my baby..??