Fetal Heartbeat?

Patient: I am 5 weeks and 3 days pregnant today. I went in for an u/s and the doctor said that there was a sac but that there was not a heartbeat and that this pregnancy would not survive. Is this too early to detect a heartbeat by a vaginal probe?

Symptoms: i still have pregnancy symptoms. i do not have any spotting or bleeding or cramping either.

Doctor: