grrr what happened? Lost everything.

Help! I really don’t know what happened. I have been working trying to get my website started. I had all my pages and was starting to blog on them. I had to do some other work, came back, word press said it had to do update and wouldn’t let me log in until it did. Then I log in and puff, my site is back to default layout and all my pages and links and everything is gone.Help. What did you do?