Unsettling thoughts/Optimism

I am now 6 weeks along after a Chemical in August. I had a miscarriage at 6 weeks for my first pregnancy in 2012, and had my son a year later. This time I actually feel somewhat calm, elated even. My first appt is tomorrow, and an Ultrasound on Dec 23rd. I have to admit, reading some posts about miscarriages, etc, really rattle me. I am addicted to this app, and reading everyone's stories. Does anyone else struggle with thoughts of "what if something goes wrong?" I try not to let those thoughts thrive, but it is still in the back of my mind. Sigh.