C.G.
At 16 weeks your uterus should only be about halfway between your belly button and your pubic bone, so I am surpised you are able to notice this. It's probably more other things being pushed out of the way than the uterus only being on that side. Everyone's body is different though, and the uterus is essentially free-floating (it is attached only by some small ligamentes, it is very mobile) so it is not that unusal to be off center a bit.