Kendall Jenner Says She's Cried Herself to Sleep Over Course of Modeling Career

Kendall Jenner's getting real about loneliness ... saying months of traveling around modeling left her in a dark place -- filled with tears just before drifting off to sleep.

The reality star-turned-mogul opened up during a convo on Emma Chamberlain's 'Anything Goes' podcast ... acknowledging she lives a very fortunate life -- but, one filled with its own set of challenges -- whether not getting a job she'd love or being overworked.

She explains she's often traveling around for months at a time ... and, a feeling of isolation can begin to creep in -- resulting in some very "dark nights."

KJ says she's found herself in random cities around the world ... sobbing herself to sleep because she's spent three months away from home without her KarJenner support system.

Jenner mentions there are times something big happens back home, and she can't go because of work ... which only adds to the sense of loneliness she feels.

As for how she gets through the feelings ... Kendall says cleansing herself -- showering or submerging herself in any kind of water -- and walks help her manage the tough times.

Kendall's been honest about her mental health ... admitting she's suffered from anxiety for years -- including diving into her recent tough months during a Vogue cover story in June.

Other KarJenners have touched on these sorts of emotions as well ... like Kendall's sister Kylie who broke down in tears during an episode of "The Kardashians" that aired last month when talking about the digs at her appearance.