irrational fears!!

I have my first scan at 12 weeks 4 days next week, and I have an irrational fear that there will be nothing there!! everyone keep s telling me I'll be fine but I'm still worrying about it!! its just scary that a a couple of pieces of plastic have told me this life changing news!! I live in the UK so no retest is done by a doctor and I've seen 3 midwives since. I feel really silly. I'll just be happy to see/hear my baby. I hope everything is okay!! am I being crazy or have other people felt this way too???