He did it with Kim K... now it's the late Whitney Houston being rumored to have nude pics and possible sex tape?

Ray J is adamant ... he is NOT secretly harboring a stash of sexually explicit photos and video, depicting him and Whitney Houston in the throes of passion -- because no such stash exists.

There have been reports ... Ray is sitting on a hoard of sex tapes and XXX photos -- holding them over the Houston family as ransom -- because he knows they're worth a pretty penny. READ MORE