Songs disappearing from my playlist, (over 100)

[zuumuu]

I have an issue with a rather large playlist of mine on my iPod, I recently had over 100 songs just up and vanish from my playlist (not undownloaded, just cut off at some random point without a trace). The last few days I've been on a bit of a new music binge so I've been saving albums and adding songs to my playlist like crazy. A lot of the albums that I'd been listening to were being downloaded as whole albums and then each song individually added to my playlist, so those ones I can track down but there were many others that I cannot track down. My iPod is basically out of space and Spotify's space has always fluxuated between 8 and 10 GBs, when I went into my storage after the songs disppeared my storage said "Zero KB", and 5 minutes later it was back up 700 MBs. So I'm wondering how I may be able to have this fixed, or at least know how to look back at things that I've listened to farther back so I can track down my songs. I'm also wondering why the size of Spotify changes so drastically and so often, I don't understand. Please Help.