Insecurities?

How would you feel if your significant other made music , before you got together and now, but listens to his old heartbreak sings sometimes still. It’s unreleased ( & actually doesn’t sound bad it’s just the message) so I don’t want to get in the way of him putting out new music. He just listens to it and sings along like he still feels that way. They broke up the end of 21 / beginning of 22. We’ve only been together 5 months so I do wonder sometimes if he misses his ex