It's not the first time Messer has accused Simms of cheating on Patterson early in their relationship.
Since mom Spears was anxious about her condition, show producers allowed for a safe word to be uttered when things get too intense for Messer.
"Me and Miranda have a normal functioning life", he said, which Leah completely disagreed with.
"Teen Mom 2" fans are aware that in season 6, the 23-year-old reality star was suffering from problems and attended therapy, and while ex-husband Simms claimed it was due to drug problems, Messer said she received treatment for her anxiety problems. They way she says it, Messer makes it seem like Simms tried to hook up with her.
Things even got so bad that Leah's ex-husbands joined forces in order to figure out the best way to ensure their children's safety. Messer then appeared to almost pass out while slurring her words and holding her younger brother's baby daughter. In the sneak preview, Messer had a heated discussion with Corey Simms' new wife Miranda.
Dr. Drew explains that the safe word is used when Messer wants to stop strong emotional responses in stressful situations.
Umm, all we have to say is... monkey? Everything will be revealed when the reunion special airs Wednesday, but sources have confirmed Messer made her accusation. In one scene, Messer was seen arriving home late on a school night, and feeding her daughters dinner just before their midnight bedtime. "Where were you at during your first couple months of marriage?"
During Teen Mom 2 Season 6, Messer was under fire for her allegedly "unfit" parenting of her and Simms' twin girls, Ali and Aleeah. Obviously, the MTV mom was alluding to their cheating rendezvous.
Watch the clip below and be sure to catch part two of the "Teen Mom 2" reunion special airing Wednesday, October 7 at 9/8c on MTV.
In a sneak peek video, Corey starts telling his ex that his current wife Miranda gave him "a backbone to stand up to your bulls**t". Should Messer bring up their sexual encounter when he was newly married to Miranda?