My mom just had a baby this past December , she's your age & they told her the same thing , & when she was about 11 wks they told her that her best option was to abort the baby bc not only wad the heart rate very low , but also because the baby had a huge chance of being a down syndrome baby . But all my mom did was keep a healthy diet & try to keep calm , bc her & my whole family thought that god sent that little one for a reason & our job was to try to take care of him & if god took him it would be for a reason too , but surprise 6 months later that baby was born 100% healthy . . . In all honesty. I think you should keep calm & take care of yourself as much as you can.
I think that the poster above me is spot on. Stay calm and take care of yourself the best you can. Change the things you can and let go of the things you can't. Easier said than done, I know...but do the best you can. If the doctors were truly worried, I think that they would be seeing you more frequently. Sending prayers.