Issue with iTunes library after consolidating

He all,

I have an issue with my iTunes library. I consolidated the library yesterday to an external hard drive, but not with the intention of using it on the external hard disk only to keep it as a back up. However, now every time I open iTunes (without the external hard drive plugged in) and try to play a song an exclamation mark appears. iTunes then asks me if I want to locate the file, so I then click 'locate' and find it in the 'itunes music' file on my internal hard drive. It does then play the song, however, when I close iTunes and open it again I can't play the song anymore. This is so frustrating! I have many playlists which I made myself so I don't want to lose all that information. I just want iTunes to recognize the original iTunes library on my internal hard drive instead of my external hard disk, and without losing all my information (so without having to delete the whole library)! Can anyone pleasssseeee help me??? Thanks in advance!