prego nurse and spotting

November 1st will be my 1 year anniversary working as an RN. I work on the surg/ortho/neuro floor and work is very heavy, I also work 12 hours shifts. I am approx. 7 weeks pregnant with my first child and recently started spotting while at work and u/s showed low fetal heart rate. I have been calling off for the past three days, per my MD's request but now I am freaking out about going back. Has anyone gone through something similar? Any suggestions?
Your best care and advice is going to be at the hands of your physician. I would follow his advice. Please take care.