Are you absolutely certain of your dates, and how long is your cycle? If you ovulated just two weeks later than the average (granted, this would mean your cycles would be unusually long), it is possible that the baby's heart would have just begun to beat at the time of your ultrasound.
If at 7 weeks it was only 11 that does not sound promising at all. I hope it will speed up but right now I would prepare for the worst. I am so sorry you are going through this. :(