Fast heart pulse days after miscarriage, thyroid problem? Or just normal? I had a lot of blood tests, do doctors have to specifically look for thyroid

Probably not thyroid. The elevated rate could be due to physical stress, blood loss, infection, or other causes. Simple lab tests should be helpful in sorting this out.
No. In your situation your heart rate is most likely elevated because of one of the following; stress, blood loss or you have not been keeping yourself hydrated. If you have a fever it could be an infection. See your doctor to review all of your results and to obtain follow up for your problem.