Ultrasound

It's a scary day. I was excited right up until yesterday lunch time, then I got scared. Today (in 3 hours) I will have my belly exposed and sound waves knocking off my bladder and, hopefully, my baby. It's ultrasound time. I'm 18 weeks and a couple days pregnant, and so far I've had no problems. But this is the first true test, I guess. And I'm scared.

What if it's a molar pregnancy? And it's already turned malignant?
What is it's an etopic pregnancy? Wouldn't I have felt that by now?
What if it's twins, and they are not growing properly?
What if it's triplets, and they are not growing properly?
What is it doesn't have all its arms and legs and ears?
What if the ultrasound tech says 'Hmmm, that's strange..." and goes to get a doctor?
What if there is no baby?
What if I have placenta previa?
What if the placenta is deficient?
What if the heart is not beating?
What if it's not breathing?
What if the ultrasound machine isn't working?
What if the tech has swine flu and my appointment is postponed?
What if there's something else completely wrong with Baby, something so rare that I haven't even read about it in any of my books?

This mother stuff is hard.