Your uterus is still below your belly button unitl 20 weeks. So, the baby must also be below your belly button. As evercheer1 said, the baby will move up as your pregnancy progresses, and then back down a little to prepare for birth. What you are describing sounds normal, but you should discuss it with your doctor if you are concerned.
I think there are a lot of factors that determine how we carry. I will say though that your baby will continue to move up as you progress. Talk with your doc and be mindful of your back if it is that you will continue to carry low.