I started showing earlier with my second one, around 12 weeks or so. But then again, I was also more bloated with the second one. I was overall much bigger the second time around.
I'm on my fourth pregnancy, with my 2nd, and 3rd I started showing around 13 weeks. I'm 5 weeks now so I have a few more weeks to start showing, but after your first pregnancy your uterus stretches and is use to having a baby in it. Remember tho all women are different:)
I'll be 12 weeks Thursday and you can tell I have a bump. Im more round than I was before and I lay down I have a bulge under my belly button. With my first I didn't show till around 8 months