iphoto says in use by another application but nothing is open

my ipoto says in use by another application:

Shut down and restart your computer, and then open iPhoto again. If the problem persists, try rebuilding your photo library. To do this, quit iPhoto, and then reopen it while keeping the Option and Command keys pressed. You can also try restoring your photo library from a backup.

I don't have a back up for some reason. how can i get my photos back.... there are thousands from our phones