I know exactly how you feel. I was so sure that something would go wrong within the first trimester for both pregnancies or that when I went for the 18 week u/s, they would say that i wasn't pregnant and was making it up (even though I already had a beachball under my shirt). Not entirely rational, but couldn't help it. I found positive thinking did wonders for me. Whenever I thought of something negative, I imagined holding my baby, feeding him or something along those lines. It was a struggle sometimes but it did work. I also stopped reading all the articles/stories about what could go wrong and focused on how I felt physically. If physically I felt something wasn't right, then off to the doctor/midwife (whoever was free first). It can be a scary time, especially the first time, but it is so worth it.