My navel piercing is moving lower as it heals?

Mine did that when I first got it done. What I assumed was that the area that was pierced was swollen and as it started to go down, it showed more of the bar. I do remember my piercer telling me that the piercing will move. The very first piercing is always longer than normal ones so that it is easier to clean and it allows the wound to heal better. What you need to watch out for is if you can start to see the bar underneath your skin. That means that your body is rejecting it and the piercing is being pushed out. After 2 years, my piercing did that. But by what you just described, you should be fine! Keep cleaning it and be safe!