lightroom catelog

While trying to clear out space on my macbook I deleted my old lightroom catelogs.

I saved the latest version but now everytime I open lightroom it's completely empty.

I've retreived my latest catelog and loaded new photos in.. saved the catelog again and then when I re-open it's still empty and I have to open my last saved catelog again. 

Did I delete something that was a necesity by accident? I can't keep saving whole catelogs to my computer everytime I use it!