iTunes > Preferences > Advanced > General > Copy music to itunes when adding to library >> Uncheck
Actually, thinking about it, if you drag and drop that imports the tunes (i.e. makes a copy). What you should do is uncheck the box noted above, then do File > Add to library and go pick your external drive
The problem was that i had another file inside the one i was transferring that also had all my music in it, hence i was transferring two copies of every song! Don't know how this other file got embedded in the original.