HELP!!! worried about my belly peircing :/?

It's normal, the skin between the bar on my piercing decreased a lot since I've gotten my piercing which was about 6 months ago. If the bar starts becoming visible through the skin is when you should start worrying, if it becomes bright red and the bar can be seen through the skin then it's probably rejecting and you should take it out asap to reduce scarring. But if it's not that then you're absolutely fine, piercings always migrate slightly.