Cathy I'm also pregnant with my first & I was a complete mess before my 12 week scan. I felt like I couldn't even get excited about being pregnant in case I somehow jinxed myself & something went wrong. I was constantly running to the loo day & night to check for bleeding. The day of my scan I was convinced I would be coming home without a baby. I never told anyone how scared I was in case people would think I was weird. Turns out that it's actually quite normal to have these feelings
So try not worry, you're not alone!! You will start to relax & become positive on your own accord. I got a good pregnancy book that had sections in it about when to seek medical help, & kept thinking if none of it was happening the baby was okay!!