Jon Jones -- 'I'm Not a Coke Addict'

UFC champ Jon Jones is finally speaking out about his positive cocaine test ... saying he's NOT a cocaine addict ... or even a frequent user ... but admits he made a "really dumb decision."

Jones -- who checked himself into a rehab facility for substance abuse after his UFC 182 victory -- sat down with Fox Sports 1 and said the whole thing was a "really embarrassing situation."

"I think a coward would sit here and try to come up with this elaborate reason ... or try to blame something. I'm not gonna do that," Jones said during the interview set to air Monday night.

"I'm not gonna blame my friends. I'm not gonna blame pressure or stress. I'm not gonna blame anything ... but what I will say is that I messed up."

Jon's mother says the UFC star checked out of the rehab facility after one night -- unclear if he'll address that during the interview as well.