Apple music - Itunes library problems

I have had Apple music for a while, no problems up until now. Yesterday, I was on my phone listening to all my music as I normally would, with no problems, all my songs were there, until I went on my Mac, into Itunes and mostly all my songs have disappeared but they are all still on my iphone? I have tried signing out and back in, it hasn't helped one bit, tried turning apple music off on my phone and back on, thats not helped either? HELP