Demi Lovato is giving her heart a break. The singer and her fiancé, Max Ehrich, have called it quits on their six-month relationship and two-month engagement, Us Weekly confirms.“The relationship has ended,” a source close to Lovato says.Us Weekly broke the news in late March that the “I Love Me” singer, 28, was dating the Young and the Restless alum, 29, after her fling with model Austin Wilson.