Sometimes fetal heartbeat can be difficut to detect, even with a trans vaginal exam, Your Doctor should be monitoring your HCG levels, this is a hormone produced only by pregnant women.Your HCG level shoul double every two days indicating a normal pregnancy, If you level does not double or has dropped this is caause for concern. The pregnancy may no longer be viable or you may have an ectopic pregnancy. Please follow up with compentent OB/GYN. I hope this helped and I wish you the best.