Dawn, I know exactly what you feel like.
When I was TTC, I wanted to be pregnant SO bad and thought it would make me so happy.
Well when I took my first test at 2 AM and saw it was positive, I started shaking and cried not because I was happy but because I was SCARED.
There is still a lot of stuff to be worried and scared about but I find myself (especially after the 1st trimester) being very happy, maybe even happier than I was before.
Your fear will eventually turn into excitement of becoming a mother.