The couple got engaged back in January 2022.
"There was obviously quite a bit of drama between them for a second, but they have been working on having very healthy and fluid communication. They have also been seeking therapy, which has helped save their relationship," the source says. "They have learned that communication is key, and honesty and trust are the key pillars to any relationship."
The source adds, "MGK has been making a huge effort and is doing everything in his power to ensure their relationship is in a good place and that Megan is happy."
As for their engagement, just like their relationship, the source says that is also "a work in progress."
"Their engagement status and wedding planning is a work in progress at this time, but they are both confident that they will be together forever," the source maintains. "Their goal is to have a happy, honest, loving, passionate relationship that they are both committed to."
Fox, 37, and MGK, 33, got engaged in January 2022, and while their twin flames were burning bright for some time with loved-up red carpet appearances and social media posts, the pair hit a rough spot earlier this year when they were rocked by cheating allegations and split speculation shortly after celebrating the one-year anniversary of their engagement.
In April, a source told ET that the couple was "taking things day by day."
"Megan and Machine Gun Kelly are doing much better and are taking things day by day," the source said at the time. "They feel like they are ultimately meant to be together, and they are working towards that goal. They believe they are soulmates and hope to build up their trust, honesty, and everlasting commitment to each other."
Since the split speculation, they've been spotted vacationing together, and Machine Gun Kelly told ET last month that Fox's Sports Illustrated swimsuit cover was "hot," while supporting her at the publication's launch event.
And last week, they were spotted holding hands in London after leaving the unveiling of the "Emo Girl" singer's ring collection, The 8th Deadly Sin - GOSSIP with Stephen Webster.
For more on the couple, check out the video below.
Pete Davidson Shares MGK and Megan Fox's 'Sick' Reaction to Joining 'Transformers' (Exclusive)