Low Fetal Heartrate?

I was seen by a midwife at 5w3d for light spotting and cramping and babe measured 5w5d nice and healthy. I was seen again at 6w3d and babe measured at 5w3d & only had a heart rate of 91. Ultrasound tech said I might be earlier than expected but I know all of my dates are spot on, I was tracking meticulously. My nurse told me “not to get too excited” and my doctor said it’s about a 50% chance of miscarriage. I’m still having strong pregnancy symptoms I’m just so terrified of miscarrying again!

Have any of you mamas had a low fetal heart rate at an early ultrasound & still had happy healthy pregnancies? I am sooooooo excited for this baby & my heart is having trouble holding on to hope!

Picture of my little peanut butter ❤️