Lea Michele believes her new boyfriend Matthew Paetz is NOT a gigolo ... he just coaches 'em.

The "Glee" actress' new man was involved with Cowboys4Angels -- a website that offers male "companionship". She confronted him about it. He copped to going on a few dates with female clients, but told Lea he only did it as research, so he could understand what the gigolos go through and coach them through it.

Lea believed him, and Matt promised he'd never do it again.

Source: TMZ