Hi L.,
What I think may be different than most, because, though I am an electrical engineer as well as being trained in midwifery, I do NOT believe ultrasound is a good idea early in pregnancy, and not usually all that necessary or even helpful later on. Here's why...especially as early as you're talking about, it's just not that accurate or capable of really telling anyone what's in there.
Remember, though it LOOKS like a picture, and it can make you THINK it's actually "seeing" something, the ultrasound is actually a constructed image from a bunch of high frequency sounds bounced off solid masses, with echoes that are timed by the machine and calculated to estimate where those echoes came from. With a six-week pregnancy---or maybe less, since you don't know EXACTLY how far along you are--things are just too small in there for any kind of accuracy or certainty that the sounds are bouncing off everything.
So, what happens when we start using all this high tech equipment in situations where there really was no medical indication, especially when it's a nurse and not a radiologist, using an office ultrasound not a big hospital one, is you get inaccurate readings, with inaccurate interpretations, and you end up all worried about things that may or may not be happening.
I think all you have the ability to do is to try to breathe, try to trust, and let Nature do what it does. You will know soon enough what is going on.
In the meantime, try to remember that until a relatively very few years ago, nobody even tried to hear a heart tone at this stage.