Kim Kardashian Says She Was on Ecstasy for Sex Tape, First Wedding

Kim Kardashian says her jaw was shaking while she filmed her infamous sex tape with Ray J, but it's not what you think ... she was rollin' on X.

Scott Disick pulled it out of her during a convo on 'KUWTK'. The mother of 3 -- who is now super straight-laced -- recalled how she used the drug during her sex scene and during her first wedding ... the one to music producer Damon Thomas in 2000.

So, to hear her tell it, those were the only 2 times she did the drug -- "I did ecstasy once and I got married ... I did it again, I made a sex tape. Like, everything bad would happen."

Kim said her wild side is still there ... "I still can do crazy things." Well, not like that.