Missing Music

I recently imported about 20 CDs into my iTunes library. They were in the library for about a week, and then suddenly today when I opened iTunes they were gone. I also used Tansee today to move some music off of an old iTouch into my library which is also missing. I also created playlists earlier today that are gone. I am so upset! I spent hours working on all of this. I have Windows 8. Help!