Looks like you’re listening on another device message

Hi All—I have an iPhone 8 and I just started receiving a message when listening to my music stating “It appears you’re listening to music on another device”. My Phone is updated, I don’t have a family plan, no one has access to my Apple ID, and the message comes up, even when I turn off my Bluetooth settings. I have restarted my phone several times and uninstalled and reinstalled my Bluetooth speaker (before I realized I was receiving the message when my Bluetooth was turned off). I’ve never had this problem - it just started 2 days ago (March 11, 2018). It’s happening both at home and at work. No other devices are being used. Any ideas on what could be happening?