When did you start showing?

I'm on baby #4 and its been 10 years since my youngest was born. I figured with such a long gap between babies, it would be like my first pregnancy where I only showed at 11 weeks. I'm on week 5 going on 6 and I'm already busting zippers on my pants. I'm much much more fit than my last pregnancies so I really thought I would be able to keep this pregnancy my own little secret for a while. When did you start showing for Baby?