Playlists were gone and anothers one created "by me"

[vinnneee]

First of all, I'm Brazilian so sorry for some english mistakes...

Today, when I logged in my spotify premium for the first time, I saw that all my playlists (the one's that i've created and followed), were gone. And other two (one with +1000 musics and other with +200) were created "by me". I did recovered my playlists, but my problem now it's that another pc shows up on the devices avaliable to play (as you can see here: http://imgur.com/a/cNJIK). It isn't my cellphone, my girlfriend's pc, I don't know who is it. I went to the "Offline devices" on the site and disconnected from all devices, but this random device keeps showing for me. I'm really worried and expect some help from you guys. Yes, I've already changed my password.