Majority of iTunes library has disappeared on iPhone SE

I've had an iPhone SE since July and had taken out the 3 month Apple Music free trial, from which I had downloaded music, but had very little on my phone as I share an iMac with my wife who is the main owner (and we can't have two libraries on the computer). I listened to my music on the way to work this morning and it was fine, however this evening all of my playlists have disappeared and I have very few songs left. I'm puzzled because 1) not all of the music has gone, but most of it, and 2) I haven't done anything to the phone in the interim so I have no idea what has happened.

Can anyone shed any light / suggest a course of action? My trial ended and I discontinued the service, so I can't just go back on and download from scratch....

Regards