Low heart rate

Hey ladies, I’m 19 weeks today. I went to see the doc because I woke up lying on my back and had a lot of sharp pains when I rolled over. She did an ultrasound and then went to talk to the specialist because when she started ultrasound heart rate was low then picked up to 140. The specialist said he wasn’t co extend because heart is still immature. I forgot to ask what the low number was. I’m kind of freaking out tho. Should I request more monitoring or something? Is that even a thing you can do?