On the January 4 episode of Married at First Sight: Afterparty, Mackinley watched back a Season 16 clip of himself explaining why he had signed up to marry a stranger.
"My parents have been married for 45 years, and that's something I aspire to have. I did think I had it with my ex. We were together for a couple of years and we were on the verge of marriage and getting engaged and all of those things," Mackinley explains in the footage.
"And then I get a text one day from her. It's a picture of her wearing a ring, and I'm like, 'Oh nice, this is the ring you want?' And she's like, 'No, I just got engaged.'"
Afterparty host Keshia Knight Pulliam could tell this subject still hit close to home for the cast member as he watched back his story.
When asked what had led up to his ex-girlfriend's stunning announcement, Mackinley recalled, "We were going on two years or something like that. And she was basically living with me at this point."
Mackinley continued, "She was staying over five nights a week, like six months prior to [her engagement]."
Mackinley explained how "a guy" had just texted him one morning, sharing his name.
"I get a text and it was like, 'Hey, I've been seeing her, just thought you should know. I didn't know she was seeing you,'" Mackinley said.
"So I wake her up and I'm like, 'What is this?' She apologizes, and I sit on it for like a day."
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
Mackinley told Keshia that he decided to forgive his then-girlfriend and attempt to move forward with their relationship.
"I'm like, 'You know what? We do have a really good connection and things are good and I've made those mistakes when I was younger,'" Mackinley shared.
"So I said, 'Well if you're serious, we'll let it slide. This is your one chance; don't mess up again.'"
But then Mackinley's world came crashing down when his girlfriend sent him the ring text.
"I get this text and it's a ring. She was like, 'I got engaged,'" Mackinley recalled.
"I was like, 'Haha! What are you talking about?' And she was like, 'I just wanted to tell you right away. The guy that I was seeing proposed tonight and I said yeah.'"
Mackinley claimed he had "hooked up" with this woman "the night before" he received the shocking text message of her engagement ring.
Mackinley went on to confirm that his now ex-girlfriend eventually married the mystery man in her life.
"And she had a kid right away," Mackinley lamented.
"And that was my No. 1 thing, like, we were big on having kids like ASAP. So literally a month later, I packed up all my sh-t, or all my stuff, and moved to California and just kind of never processed it."
Mackinley admitted his appearance on Afterparty was probably his first time talking about the situation and his heartbreak, given he had never confided in his parents, family members or friends about it.
"That was my first time speaking on it," Mackinley confirmed.
On Married at First Sight's Season 16 premiere last week, Mackinley said he moved from Michigan to Nashville and was staying at his best friend's place.
Mackinley apparently dropped out of college and started his own business, and he said he was ready to find love and settle down.
"I want a long-term life partner, somebody to bring me out of my shell," Mackinley explained.
Meanwhile, Domynique described herself as a mature woman. She's an only child to a single mother, who is her best friend.
Domynique said she spoke to her mother multiple times a day, even on her lunch break at work, and her mother signed her up for Married at First Sight after a string of bad dating luck.
"It just seems there's a lack of commitment... and so what better way to avoid that than going into a process like [this]?" Domynique told the cameras.
Married at First Sight expert, Pastor Calvin Roberson, said Mackinley and Domynique have similar attachment styles in relationships in that they both like their independence and would be turned off by an overly needy or immature spouse.
Mackinley also asked for an optimistic and outgoing partner like Domynique to expand his horizons.