Baby heart rate 🍼

Im nervous because i went to the ER and they told me i was 5w and that the baby heart rate was low and if it doesnt go up i could have a miscarriage it mine and my fiances first baby and we all are really excited just hopin that the heart rate is good . i started prenatal vitamins this morning but not sure if it going to help . go doc appt tomorrow to check the heart beat lets just hope its not low and gone up !!!!