"They have had issues in the past, but things seem pretty serious this time," a source tells PEOPLE Megan Fox and Machine Gun Kelly haven't officially pulled the plug on their wedding plans.

Los Angeles, California (CNN)-- "Transformers" actress Megan Fox said "yes" to ex-fiance ... that she dropped the 2-carat diamond engagement ring into the sand, Us Weekly magazine reported.

Chatting to Christine, Megan revealed she was "loving wedding planning," however ... Megan adorably revealed he'd be taking on the role of ring bearer for the upcoming nuptials.