Cloud wiped out all of my good music?

I've downloaded a lot of old CDs and mixes my friends have given me, and I actually have been pretty happy with my music. A long time ago, I used cloud to back up my music but I stopped a while back. So today, I went on to listen to some music, and all of my songs aside from the ones saved on cloud (Most of them I don't even listen to anymore) were gone! I had so many, and I've given back most of the CDS. I tried logging out of my iTunes account, but then there was no music at all...? I don't know what else to do. Please help.