Low heart rate?!?!

Ashly

So I discovered I am 6 weeks and 5 days along in my 3rd pregnancy. (I miscarried my last 2) I had gone to the ER because I was having pain in my left flank. The ER doctor said my baby's heart rate was low for what I was measuring at. The rate was 87. I am panicking. I don't want to lose another baby. Has anyone had a low heart rate and still went on to have a healthy pregnancy???