Lea Michele -- Shacking Up With Ex-Gigolo Boyfriend

Lea Michele's new boyfriend isn't a fun summer fling after all ... officially ditching his gigolo lifestyle in order to move in with the "Glee" star full-time ... TMZ has learned.

Sources close to Lea tell us ... Matthew Paetz packed his stuff into a U-Haul over the weekend ... moving out of his apartment, and upgrading to her $1.4 million Hollywood pad after just 4 months of dating.

We're told Paetz already had a toothbrush and a few t-shirts at her their place ... but now everything's been moved -- rugs, furniture and even his pillows.