Oh Sharyn, what an ordeal to go through. So sorry for the loss, but I am so glad you have seen this baby's heartbeat, that's a good sign that all will be well
The same thing happened to my SIL. She was even scheduled for her D&C and they did one more u/s just to make sure....and there was that hearbeat beating away - her baby boy is now a happy 18 month old! I also had an experience like that - one ectopic and I also m/c along with the e/p so I either had a "pseudo-sac" that can happen with e/p or one in the right place and one in my tube.
I hope you have no more scares and you are able to enjoy a nice and easy pregnancy. How far along are you?