I'm 13 weeks should I be showing already?

So yesterday I walked past my bfs family, I was wearing shorts and a tight shirt, I have a small belly that only me n my bf can tell, but when I walked passed his family after I left all I can hear is them saying she's not even showing yet n I go outside n I tell them I'm 3 months 1/2 n they were all asking why I'm not showing and now they got me all worried, should I be concerned ? I'm petite I'm 5'2 and weight 130 when is it normal to start showing ??