ubun2

I installed Ubuntu on a core i5 laptop about a month ago. After a few days the network icon was missing in the panel, and I could not retrieve it. Because I had no way to get on-line through Ubuntu I decided to re-install the version above mentioned, then 3 or 4 days after the new installation everything was running well until I received a notification for updating the system. I did what almost everybody does, (password and so on...). Everything continued to work well, then I shut down the machine and the next day after starting it, I noticed that there were no directories in the home folder, Music, Downloads, Videos and some others were missing and are still missing. The only one left was Desktop and now everything shows on it, I mean, if I download something from the web, if I create an Open Office document, if I change the desktop background. I honestly know almost nothing about Ubuntu-Linux, so please any indication would be greatly appreciated.