I have had this before, and it is a yeast infection. It can be very painful. While antibacterial soap helps by keeping it clean, it does not get rid of the yeast. Yeast is a fungal infection, and you will need to use a topical to kill the fungus. It would be a good idea to go to a doctor for a prescription cream. Make sure that you keep your navel clean and dry. If you work out or are doing activity that causes you to sweat, make sure to dry your navel, or it will come back. Try not to wear clothing that is constricting around the navel. It's similar to having athlete's foot, but it's on another part of your body.
it is either your period starting, or you have a hernia hidden inside behind the belly button.