Invalid My user got hacked, help

Hacker's Steam Name: nylevii
Steam ID: STEAM_0:0:10756911
Evidence:‏ Tradelog. When i logged on today it said someone else had been on my account from Rogaland, norway. I logged onto team fortress 2 and found out my earbud was gone.‏ And this drading took place when i was at school.
and it said i had been trading with a guy named nylevii‏
This is his information thast i could gather about him:
located in: STAVANGER ROGALAND NO
Heres the guys pc IP: ¨109.247.66.233¨
steam account url: http://steamcommunity.com/profiles/76561197981779550

How this happened:

When i came home from school i went on my pc and when i tried to log on my steam it said that another pc was logged on my account and i freaked out. I checked my email and it was an email from steam that said that this guy was logged on my account from a different place. He's pc ip was there and everything. I play Team Fortress 2 and i had just got this Earbud that i was very proud of. Then i got afraid of that he had taken that so i checked my inventory and the bud was missing. I checked my trading history and it said that this day 17 December 2013 i had traded with him, when is was at school... and that i had given him my earbud and a botkill scattergun and he had given me some items from dota 2 that i don't even play. It said that i had traded with a guy named: nylevii
I checked his back pack and he had 2 Bills hat and another rare hat and 5 other items i dont know what is and the funny thing is that u should usally have a little bit stuff in ur account if u have 2 Bill's hat cus they are really exspensive so i believe that i am not the first he has scammed.
Please help me.

Please report this to Valve as they are the only ones who can assist you in recovering your items.

As there has been a change in SR Policy: http://forums.steamrep.com/threads/notice-changes-to-investigation-policy.47952/

I'm marking this report as invalid, please read over the thread I've linked for further information.