Low fetal heart rate

I was having some spotting yesterday and my midwife wanted me to come in to get an ultrasound. The ultrasound measured me at 6w1d the same as last week. The baby's heart rate was only in the 80's when last week it was 100. I'm so scared of losing this baby. Please pray for me and provide any positive feedback if you can. I should also mention the spotting is light and brown. The doctor didn't even take a swab of it because there's so little.