MTV Star -- I'm Raffling Off My Moldy Vagina ... On Webcam Site

"Are You The One" star Alex Kim is living the Hollywood dream ... and by dream we mean she's raffling off a mold of her vagina to dudes on a nude webcam site.

Kim -- a contestant on the MTV dating competition -- is pulling double duty ... she's also a webcam model on a popular XXX site.

We're told Alex has been webcamming long before her first TV appearance -- the show's finale is Monday -- but never told producers. Now she's exploiting her fame ... by including the MTV credit in her username.

But the craziest part ... check out this ad on her page for an upcoming raffle.