Singer/actress Jessica Simpson's on/off relationship with rocker John Mayer has ended. The couple announced their split last month (May07) but have since reconciled. However, they have now reportedly separated again. A source tells website, "They broke up Sunday (03Jun07) night, but who knows what the future will hold. "This is the twelfth time they've broken up. Their relationship is volatile. Last week they felt better than ever. This week, things are rocky. Who knows what the future will bring."