Can you ring and rearrange? With my first pregnancy I called the hospital because I couldn't make the original appointment. Surprisingly they offered me an earlier date putting me at 12wks 4d (my birthday actually - best bday ever lol). I have my first ultrasound on Monday, I'll be 12+3. Best wishes to you.
I'm 9 weeks pregnant and im quite disappointed that I have to wait till 13 weeks to get my dating scan i'm like you i'm impatient too this is going to be a long wait
If you're really anxious you can always go to the er saying you have bad cramps. They'll do an ultrasound and can probably tell you how far you are