Fetty Wap's Ex-GF Alexis Sky Accuses HIM of Leaking Sex Tape

Either Fetty Wap or his current chick is responsible for leaking his sex tape with ex-gf Alexis Sky, according to Alexis, anyway ... who's now issuing her own legal threats.

TMZ obtained a copy of the cease and desist letter Sky's attorney fired off to Team Fetty -- after he sent one to her -- and it squarely accuses the rapper of putting the video out on the Internet. The way she sees it, it was most likely "released by someone gaining access to the materials through him, with or without his knowledge."

Of course, he's accusing her of the same -- so it's a whole lot of finger pointing right now.

But here's a twist -- Alexis went on the 'Breakfast Club' Wednesday morning and hinted Fetty has a bunch of sex tapes ... with other chicks.