IGive up with this iTunes?

I've been trying to figure this out and i'm going crazy and need help. My itunes on my new computer is for some reason super outdated and doesn't match my current iphone AT ALL. It has some, but not even close to all of my music. I have so much more music on my iphone that I have accumulated over the last decade. So I bought a new CD and ripped it into my itunes by now it won't let me move it to my iphone. If I sync my phone to my itunes the only available options will wipe my phone and match it to my current itunes (which as I mentioned doesn't have a ton of the music found on my iphone).

Best thing to do is, make sure all the music on the phone is backed up, either to your computer, and external flash drive or the cloud. Once this has been done, then delete all music from the phone and RESTORE from the non phone storage back to the phone.

Then once a month or so, make Backups from your phone to the computer, find the backup file and rename it to something you can remember and store a copy somewhere that is NOT your phone or your computer.

The reason why I say backup vs syncing, is that most people do not look at the sync settings, which tend to make either the phone or the iTunes computer files the master copy, so this may often make the least updated version of your files that over writes and replaces what is on the phone. When you do backup and restores, you have a filename and date to remind you which copied are older/newer.

I personally have not had the issue you are having because I backup and restore rather than sync.