iTunes won't sync music to iPhone 6s with ios9.2.1 - help!

I have a new iPhone 6s+ and iTunes 12.3.2 on my Windows laptop which is running Windows 10. When I go to sync it to put my music on my phone, it starts and then doesn't finish. When I first tried, it gave me an error message saying there were problems with 100 songs that were unable to sync (many of which I purchased through iTunes, so that makes no sense). I figured it would then sync all but those 100 songs, but it just quit the sync process. After repeatedly getting the same error message, I clicked "Do not warn me again." So I think it's still doing the same thing without the warning message. I even quit and restarted iTunes a couple times to see if that would help but no luck. Twice now it's acted like it's syncing properly and then gets stuck on Step 5 of 5 - "Waiting for changes to be applied". Also, on the computer on iTunes, the little rotating arrow-circle indicating syncing is present, but it doesn't show up on my phone, just the rotating asterisk, for lack of a better term. Help?