How did you hide your pregnancy?

I miscarried with my last pregnancy, so this time I plan to tell family and friends at 11-12 weeks and announce on social media when I know the gender. I'm almost 5 weeks. My birthday is this weekend and with the holidays coming up, people are going to wonder why I'm passing on drinks and stuff. My sister always buys rounds of drinks for my birthday and they'll definitely think something is up if I just suddenly don't have anything. I want to shout it from the rooftops but the disappointment last time was too much so I'm really set on waiting.