How are you "losing" music? I've been using iTunes since it came out and haven't ever lost a song, syncing across computer, phone, iPad, etc.
Just add it into your library, and then use playlists and etc to sync the music on your iDevice. Just remember that your iTunes library is the "master" version.
Are you trying to manage your music another way (i.e. ouside of iTunes)? If so, how?