I had a belly piercing before. mine got infected which turned into an abcess because I removed the piercing for a few hours and it closed up. It really does sound like a normal infection. Use the salt water mug method for the 15 minutes each day until it clears up. Whatever you do, don't remove the piercing unless your piercer or a doctor tells you to.
It might possibly sound like inflammation. It might be because your shirt or whatever has been rubbing against your piercing causing it to irritate your skin, or maybe you're just healing a lot slower than normal? I'd pay attention to it and clean it often though.