Really do try not to worry as stress can bring such things on, yes many women do have a miscarriage early on but a lot more women carry successfully.
I miss carried with my first at 11 weeks and worried with my second although everything was fine and now I have a three year old, Im now 3 months pregnant and have only just found out so its a bit late to worry!!
Just look after yourself take folic acid and any extra vitimins you need and eat well that way you know you are doing everything you can to help your child, you cant do anymore than this, it is out of your hands. When you feel you are sressing about it take your mind of things by talking to someone or doing something to keep you busy. Before you know it you will be 9 months, over due, fed up with being pregnant and just wanting the baby out, wondering what you was ever worried about.
good luck and congrats xxxx