How to add music from another computer (iPhone 5)?

My laptop broke and had all my music on it and now i'm trying to use a different computer to add more music but a message keeps coming up saying that I have to dleete all my previous music in order to get new music.

I don't purchase my music off of itunes so is there anyway i could add music without deleting my other music?

Its doing that because iTunes music not purchased and loaded from a computer is only a shortcut. Once the music you had is no longer on your computer or moved to a different directory iTunes can't find it so syncing iTunes will delete all your old music.

If you want it again you need to reload it from scratch sorry. That's how iTunes works.