Should I be concerned?

I'm 17 years old and am around 13 weeks. I haven't been to the doctor yet, but will soon. I've recently began taking prental vitamins and calcium vitamins and drinking water and trying to exercise more by taking walks. I know it's typical to be worried about complications with the baby but should I be too concerned about birth defects or anything like that? (I worry a lot) nothing like that runs in my family either, I'm just really worrying about the baby and would like to know of I should be as worried as I am