Megan Fox and Machine Gun Kelly’s rollercoaster romance is back on track after overcoming another rough patch. According to a source, the stars are “fully back on” after taking some time apart earlier this year. “They’re really enjoying each other and getting along better than they have in [months]. The distance was good for them,” the source told a magazine. “They missed each other.” MGK, 34, and the Jennifer’s Body star, 38, have made a handful of public appearances lately, most recently attending Michael Rubin’s Fourth of July party together in the Hamptons. It’s unclear if the stars consid…