Announcing pregnancy?

Andrea • Baby boy born 2015, excepting babe #2 in April 2019!
When is everyone going to announce their pregnancies publically? I want to announce at 12 weeks and today I was talking with my coworker and she said I should wait till 20 weeks. I kinda got mad and I don't know if it's my hormones acting up but it made me sad. How could I possibly wait that long? Does that seem like not her place or am I over reacting? I feel like I should be able to announce it anytime I want after 12 weeks but now I'm feeling down about it.