Hi, I would not give up hope I would rest as much as possible. We had odd fetal heartbeats in early pregnancy and some spotting we now have our son. These tests are not always conclusive. I would try to relax and give this little one the best chance. Good luck hope it works out for you.
I'm so sorry for what you are going through.
Sadly, in the first trimester there is rarely if ever anything that can be done to reduce the chance of a loss. Some Dr.;s will prescribe bed rest, etc, but studies have shown this does not change the outcome. This is because almost all first trimester losses are due to a chromosonal abnormality. The second leading cause is believed due to environmental issues such as drug use or chronic drinking, but that is rarely the case and I am pretty confident that is not the case with you. It is also untrue that stress causes miscarriage. For the most part it either happens or doesn't. In all honesty, with lack of growth and a heartrate that slow this does not look promising. I'm so sorry, I know how agonizing this is and I truly hope I am wrong. I wish you well, and know we are here if you need to talk to others that have been through this. Sadly, many many women will experience at least one first trimester loss in their childbearing years.