Family Unaware

Currently I'm 21 weeks pregnant and very few know. My SO's family only has 3 people who know and my own is 0. I am starting to show and I have yet to figure out a way to tell the families. I regularly avoid social situations and stay home to watch my son. As much as I love my SO and his family they made my last pregnancy hellish. I just need advice on how to tell everyone without avoiding another party or upsetting someone by keeping it all a secret.

* My own family lives 5 hours away and already hate that they miss a lot of my sons milestones.

*Also still don't know gender yet