the first 12 weeks are when you are at a greater risk of miscarriage, but this is at its highest at the early stages. Many pregnancies end before a woman would even know she was pregnant.
The symptoms you are experiencing should reassure you that your pregnancy hormones are increasng all the time and your body is making changes for the future months.
I think all pregnanct women worry for those first 12 weeks and then, even after that, find other worries to occupy their minds. Its perfectly normal but with each week that passes the chances of complications decrease.
congratluations!