Demi Lovato's Ex Max Ehrich Dropping Single About Their Relationship

Demi Lovato's would-be groom is pouring his heart out on wax ... with a love song about the first time he met her ... something we're guessing ain't gonna please his ex-fiancee.

Sources with direct knowledge tell TMZ ... Max Ehrich is dropping a new single Friday, and it's all about his relationship with Demi.

We're told the tune is about the night he met Demi, and it tells the story of his inner dialogue -- being terrified of falling in love with her because he knew their relationship was the real deal.

Our sources say Max's song also touches on him falling for Demi right off the bat, and he sings about how he couldn't sleep because he knew he wanted to be with her forever.

As you know ... things didn't work out between them, and Demi recently leaked a song about their breakup. For his part ... well, he went ham, first saying she never really broke up with him because he learned about it in the tabloids, and then somehow invoking Jeffrey Epstein's name in their relationship.

It's interesting ... we're told Max recorded the song in quarantine, in a makeshift studio inside the home he was living in with Demi. So, exactly when did he write this song?

Max's album won't come out until next year -- he signed a music production deal last October before he started dating Demi and finished the second half of the album after meeting her -- but our sources say he wants to drop the single now because of how he feels.

Max's track is set to debut on all streaming services.

As we reported ... Max spent part of his weekend sulking on Malibu beach where he proposed to Demi ... he calls it a "healing experience."

Our sources say Max still loves Demi and while he's doing all he can to move forward, the split's been very painful for him.