Jerome McCoy -- who goes by "Legion" on Reesa's now-infamous 'Who TF Did I Marry?' video series, which is at least 50 parts deep at this point -- tells TMZ ... everything Reesa, whose real name is Teresa Johnson, declared about him in her lengthy video series is false.

While Reesa made many allegations against Legion -- including claims that he fibbed about his career, family and wealth, etc. -- he's hitting back with accusations of his own.

Legion claims he and Reesa were having trust issues at one point -- and goes on to claim she attempted to reconcile with him while allegedly threatening to "expose" him if he did not comply ... and he suggests him not budging is why this is all coming out.

It goes without saying ... Reesa's ex is feeling the backlash of the TikToks going viral and claims it's hurting his job in PR -- which he says he does for a hospital. Amid all this attention, Legion tells us he met with attorneys Monday at work to discuss taking legal action against Reesa -- on its face, it seems his company believes they mighta been damaged by her storytelling. Legion says he's supportive of any moves they might make.

Unclear if he's considering private counsel for himself at this point ... but he's certainly mulling his options right now. Bottom line ... Legion tells us the way he's been portrayed by Reesa is NOT who he is at all -- and he feels he's been wronged by the tale she's told.

There's no denying that Reesa's videos have been a huge hit online ... with one video garnering over 11 million views on TikTok. Reesa's account also boasts nearly 32M likes.

Actress Danielle Pinnock -- from the TV show 'Ghosts' -- has already pitched herself to play Reesa if the viral saga ever gets a small screen adaptation ... and something tells us this thing might just get made into a movie or show down the line. Indeed, it's that wild.