Cory Monteith and Lea Michele were "happy," "in love" before he died. Credit: Amanda Edwards/WireImage

Things seemed to be looking better than ever for Cory Monteith before he passed away suddenly at age 31 over the weekend. Indeed, the Glee star and his costar/girlfriend Lea Michele were ready to take things to the next level, a source reveals to Us Weekly. "Lea and Cory were planning on moving in together after he got back from Vancouver," says the insider of Monteith, who was found dead in his hotel room on Saturday, July 13.

Dating since early 2012, Monteith and Michele, 26, "weren't talking engagement or marriage yet but it was heading that way," explains the source. "The first step was Cory was going to move in [to Michele's L.A. home] completely. He was already there all the time."

Despite some speculation to the contrary, the couple were anything but estranged before he died. "They were 100 percent happy and together and in love at the time of his death," the source clarifies. "They never broke up."

Grieving in private, Michele has yet to release a statement on the tragedy. "We ask that everyone kindly respect Lea's privacy during this devastating time. Thank you," her rep told Us.

With his love in L.A., Monteith's final week in his home city seemed a tranquil one. "Cory had just been hanging out with friends and seemed in good spirits, his usual self," a Vancouver source says. An onlooker noticed on Friday -- one day before his death -- Monteith "and a few friends" were spotted leaving the Fairmont Pacific Rim Hotel. He returned to the hotel alone later that evening.

An autopsy is expected on Monday.