I agree with the girls, we had to have an internal u/s with DD1 and she was 6wk5d and we saw the faintest of heartbeats, the sonographer said had we done the ultrasound the day i had my bleed (4 days before) he thinks we wouldn't have seen it anyway.
She's here now and safe.

Please stay positive and remember it's natural to feel worried and don't feel bad for calling your Dr, it's what we do, were mothers and we stress before their born, when their born and when they are 40yrs old
Enjoy your pregnancy and wishing you a happy & healthy 9mths