Trying to keep it secret....!

Emma
I wondered if I could ask people's advise with this....
I only found out I'm pregnant less than a week ago, so it is still a secret from family and friends.
I've been invited to a friends birthday party tomorrow night, and won't miss it, as they are good friends. However, what excuse can I give for not drinking alcohol that they won't then get suspicious and guess I'm pregnant???!
We only got engaged in Christmas <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> too, so they were already suspicious we got engaged because I found out I was pregnant (wasn't true at the time though!)
Any help would be greatly appreciated!