I was nervous all throughout with my first. It eased up a little after the first trimester just try your hardest not to dwell on it. Its natural what your feeling.
It's completely normal to have that feeling.. 1 in 5 early pregnancies do result in miscarriage but, that does not mean you're doing something to cause it. As long as you cut out cafiene, alcohol, smoking (if you do) eat healthy and take your vitamins, you're doing all you can do. Try to relax and enjoy it the best you can. This week is when the heart beat can be seen so, if you go for an ultrasound that might help to ease your mind.. Best wishes
if this is your first pregnancy and you havent had any miscarriages, there is a 5% chance of misscarriage once pregnancy has been confirmed by ultrasound, once they see a heartbeat (or about 6-8 weeks) there is about a 3% chance, after 12 weeks it goes down to 1%. the one in five thing is including all eggs that get fertilized and lost before implatation can occur properly, dont freak yourself out ;) be happy