People and my stomach

Lynzee • Mommy to Ammarie, born on March 3,2016!
So, I've gotten to the point where I have a tiny bump and people assume it's okay for them to just rub my belly. 
I went to a restaurant that I used to work with, and one of the girls tried to rub my stomach and I just kind of stepped back and said I felt sick and if she touched me I would puke lol 
But, for real. How can I tell people nicely not to touch my belly? I don't want to be rude.. But it feels weird for other people, especially people I'm not close to, to want to touch it.