"It's the classic story — things were really hot and heavy in the beginning, but now the infatuation's worn off and their differences are showing," spills an OK! source.
The Transformers star, 34, and "Bad Things" rapper, 30, who hooked up last May after Fox called it quits on her 10-year marriage to Brian Austin Green, "are still putting on a good show in public. But behind closed doors, there's been a lot of bickering and even a few fights," continues the source. "Megan and MGK aren't giving up on each other just yet, but they're going to have to work hard on their relationship if they want to stay together for the long haul!"
Fox and Kelly may be holding onto some previous baggage, ultimately putting a strain on their relationship. "Megan may be gorgeous, but she's got insecurities, and MGK has his fears too," says a source. "There are things they both need to work on."
As OK! previously reported, the father-of-one admitted that he was “coked out of his mind and in a drunken stupor” when he began working on his latest album, Tickets To My Downfall, which he released last year. At the time, however, he said that being with Fox during the process of putting together the project helped him make some vital changes as far as his health was concerned.
"I did fall in love during the making of this record, and I did become a better person,” he said of Tickets To My Downfall. “It’s interesting. There was probably a crossroads in the middle of making this album where the title would have lived up to the reality.”
As for Fox, she's recently seemed eager to have her divorce from Beverly Hills, 90210 alum Green finalized, so she can move forward with her new beau. A source previously said that she and the “Bloody Valentine” rapper “plan to be together forever.”
However, the source pointed out how Green was delaying the process. When it comes to finalizing things, Green is "definitely not making it easy or doing things quickly," the source said at the time.