Are you worried incase there is something wrong with your baby as oppose to the actual "birthing experience" 
I'm pregnant with my 3rd child and like Lawlaw i knew by 5 or 6 weeks with all of mine, all i can say is that they really can tell an awful lot from scans, a lot more than we can see from them. Despite knowing earlyish with mine it does not stop me worrying, it's only natural to worry that there might be something wrong with him/her and unfortunately you won't know until the big day arrives.
I think unless you were drinking a lot everyday there is no real evidence to suggest that alcohol when pregnant harms the baby - although common sense and guidelines tell us to stop drinking. I'm sure that once you did know you took all steps to ensure the health of your little girl. There isn't anything else you could have done.
Try not to worry too much, i'm sure everything will be fine and she'll be the most adorable little bundle you've ever set your eyes on.