Tips on keeping pregnancy a secret?

Br

I’m 4 weeks 6 days today!

On Thursday I have to travel for work with a group of women. While they don’t go out to bars or anything, we usually do share a bottle of wine at dinner. I’m afraid if I deny that they’ll be onto me and my boss will be there who I do not want to know yet!

I thought I could say I felt dehydrated/had a headache but that seems fishy for more than one night.

Any tips?