I've never had it, but I know it's quite common, especially with pierced belly buttons, but can happen in people without piercings.
It's a hard infection to treat, because the bugs get all closed off in little sacs, and the antibiotics often can't get rid of them all, so they grow back! This time, get your doctor to put you on a longer course of antibiotics, and use some antiseptic cream (ask the chemist) on the area, and hopefully that will work.
(p.s. am a doctor, but only just qualified, and i can't see you or examine you, so obviously if you have any big queries you gotta see your own doc