I think it's really normal to be scared when you become pregnant. I had all the same worries during my first 3 months. Even though millions of women have babies all the time, its still a massive deal when it happens to you!
Did you know that your hormones are all over the place during the first trimester and that its likely that they will settle down during the second?
That could be contributing towards your feelings of not living up to your expections when the baby comes along.
I had a friend who, throughout her entire pregnancy didn't want her baby at all. She was adament that she wouldn't love it or be able to all the normal mum stuff when it came along. But when it was born (about 6 weeks ago) she just knew what to do, held her baby straight away and now says she wouldn't change it for the world!
I hope the above has helped a little. Good luck, rest as much as possible and take care.
Angel x