btwittey - Firstly congratulations on your pregnancy!
With regards to your drinking, there is nothing that you can do and no way of knowing what if any effects it will have on your bubba.
The fact though that many women do not know they are pregnant until well into the first or second months and many don't know until much later (or until they give birth!) means that many of us engage in activities that are not altogether healthy for us of growing babies, without ill effects, indicates that there may not be any impact on the bubba.
I know this does little to allay your fears, but take some comfort in knowing that many women have gone before you, and consumed much more than you and have borne healthy happy and complete children
When you go for your scans through your pregnancy they can do tests to show if the baby is malformed or suffering major illness, and although not perfect they do help to ease the stress.

The best thing you can do is to live a healthy lifestyle for the continued pregnancy and know that you are doing the best you can to grow a healthy child

try not to stress hun - there is nothing you can do about the past, you can only change the future.
Enjoy the experience hun, it is over all too quickly!

And Welcome to BB!