Megan Fox Unbothered by MGK Moving on With Dakota Johnson

Megan Fox isn't losing any sleep over Machine Gun Kelly spending time with Dakota Johnson ... 'cause we're told Megan's put their former romance firmly in the rearview and has bigger things on her plate.

Sources familiar with the situation tell TMZ ... Megan is completely unbothered by MGK moving on with Dakota, and she's got no interest in getting involved in his love life.

In fact, we're told Megan and MGK still have no relationship outside of co-parenting their 1-year-old daughter, Saga Blade Fox-Baker ... and Megan's completely cut MGK off unless it's something involving their little girl.

As for Megan's own dating life, sources say she's currently single and keeping it that way ... focusing on being a hands-on mom and making money.

And she's already putting in work on that second part ... recently launching her exclusive content page on Subs.com, giving fans a chance to see a whole new side of the actress ... not to mention her new ad campaign for telehealth company Ro that's been all over TV.

Meanwhile, MGK and Dakota have been spending time together ... last week Dakota was spotted waiting for the rocker outside a Los Angeles recording studio ... and in September, the two were also seen together in New York City.