Themes and Plug-ins Suddenly Disappeared!

Hi, I was wondering if any of you can help me.

The themes and plug-ins that are installed on my WordPress suddenly disappeared! I can’t figure out how or why, I recently updated to WordPress 3.8.1 but I am kind of hesitant about it being the cause. I have updated two to three weeks ago, and there had been no problems until today. It’s my first time to encounter problems on my WordPress and I don’t know how to bring back all the missing installations.

I tried to re-install the plug-ins and I was able to, but when I activated them, WordPress says there are errors. I searched for the plug-ins and tried re-installing them but it says they are already installed. Same goes for the themes ??

I read on topics in the forum and they say the site could be possibly hacked.

Hope you can help! Thanks!