Iphone keeps saying I'm synced with another library?

My family have an itunes account that we all use, though it's mainly my parents. When I want to add music to my iPhone I add it manually then delete the files so that it doesn't sync onto my parents iPods. When I plugged it in this time, it claimed I'm 'synced with another library' and didn't allow me to select manual selection and won't let me add music unless I sync the WHOLE itunes library and delete all the information on my iPhone.

I have no files I want in the itunes library, and I can't get some of the files back that are on my iPhone. I don't know how to get around this and I can't afford to lose all my data. Does anyone know anyways to fix this?

Try connecting the USB the right way round, dust sometimes affect connection and therefore affects the iTunes.

Go Into iTunes.
Click The Store Tab At The Top
Click On Authorise This Computer
Then Put In Your iTunes Login