Am I showing?

I've recently had to tell several people that I'm pregnant. (for work health reasons, it's best if my supervisors know, in case something were to happen). One of my principals simply could not believe it when I told her I was almost 4 months along. She said, you couldn't tell, you don't look it. Well, I'm hoping people start to think I am naturally and not just that I've put on a little weight. Tonight I had a tell tale sign. My apron I usually use I wrap around me once to the back and then tie it up at the front, usually no problem...tonight, slight problem. I could still do it but not as comfortably as usual. I'll have to get a mid pregnancy shot soon and post it up.