What Causes Itchy Red Ring Near The Navel?

Hey, I'm a 5'5, 15 year old make weighing 9 stone.I have noticed an itchy red ring appear about 3 inches to the left of my belly button. It has grown a bit and in the centre the skin is slightly yellowed. ALong with that itchy red spots have appeared on my torso, back and upper legs. Any ideas??