Can't sync iPhone playlist with iTunes and vice versa...

My iPhone 6 plus is really frustrating with me. In the past, when I created a playlist on my phone, the playlist would automatically show up in iTunes the next time I started iTunes. But recently, playlist I created are not showing up in iTunes automatically, so I tried to manually sync my phone's playlist, by plugging my phone into my computer and syncing my phone via USB cable. Unfortunately, the syncing did not work---There are purchases on my phone that are not in my iTunes library and there are playlist (and songs) in my iTunes library that will not sync to my phone. After tinkering around with this for several days with no success, I decided to start all over by restoring my phone and starting from scratch. But when I attempted to restore my phone, I received and error from iTunes stating that there were purchases on my phone that are not on iTunes and if I proceeded with the restore, the purchases in question would be deleted and I would have to purchase the items all over again. (???)

I all want to do is transfer all my media (and playlist) that exist on my phone to iTunes (and vice versa), but I can't do it---my iTunes library and my phone do not match and I have media on my phone that is not in my iTunes library (and vice versa). Syncing my phone to iTunes does not update my phone or iTunes so at present, I'm stuck. For example, I currently have a playlist on my phone that has 240+ songs in it, but that same playlist exist on my PC in iTunes and that playlist only has 40 songs in it!

ARGGGHHH!---so frustrating!

Any assistance would be greatly appreciated.