19 weeks uterus not growing?

K
Hi ladies I am nearing 19 weeks and I still don't have any type of bump. Even when I lay down I am completely flat. I am overweight. It still feels like my uterus is still very low right above my pubic bone. This is my first baby. Should this be a concern? I have heard of IUGR and women's uteruses just not growing at all...