I have had my belly button pearced so some time now (over 5 years ).Over the last couple of days it has become really itchy and smelly and looks like pus is coming out.
its infected and its a bit unusual since youve had it so long, as it should be fully healed by now so youll need to get it checked out by a doctor or a profesional piercer but mainly the doctor who can give you things to clear the infection
You may have an infection see your Doctor asap.