Empty egg shells in a carton of eggs that hasn't been used....?

I bought a dozen eggs about 2 weeks ago, and I went to go and use my eggs today. Now, when i purchase eggs I always check them first, and they were all in tact. However, this morning when I opened up the carton to use some eggs, 5 of them were cracked. I was worried that I was dripping egg all over but then realized they were almost all empty..no yolks in them, just a little bit of white. I immediately checked the refridgerator to check and see if egg had been leaking out of this carton onto everything (of course I feel i would have noticed them at an earlier date) and of course there was no mess, no egg stain on anything, nothing. what the hell is up? I'm confused? How did they get cracked, and where did the insides go? And, there are 7 good eggs left, should I use them?