Titans star O-lineman Taylor Lewan straight-up cried on camera Wednesday ... and it's all because he says he accidentally ingested a banned substance that could lead to an NFL suspension.
Lewan -- Tennesee's 3-time Pro Bowl left tackle -- is facing a 4-game ban after the NFL says he tested positive for ostarine -- a substance that essentially works like anabolic steroids.
Lewan made a video to explain the situation ... and adamantly says that while he did NOT knowingly take the substance -- he is responsible for it getting into his body.
"I want everybody to know that I've never taken this supplement knowingly and I've never cheated the game and I never will.