'Love & Hip Hop' Star Stevie J -- Joseline Cheated On Me -- WE'RE DONE!

"Love & Hip Hop: Atlanta" star Stevie J has HAD IT with his partner and TV co-star Joseline Hernandez ... telling TMZ it's over because she cheated on him.

Stevie claims she's hooked up with not just one but several rappers. He tells us he found out 2 days ago and says he had overwhelming proof ... enough for him to dump her.

Joseline is off the radar ... nowhere to be found. We've tried calling her for a response but she's gone radio silent.

It's a sudden turn ... just last week our photog got them leaving an L.A. restaurant hand-in-hand. And just last Saturday he serenaded her at an Inglewood club ... proclaiming his love for her.

Stevie was arrested last month because he's more than 1 million in the child support hole.