dont log in in facebook for 2 jears .... it will stop....

no really ..... open a new acc and look with that second acc if your status updates again.... WITHOUT TO LOG IN IN THE ORIGINNAL ACC!! (dont forget to friendship them...)

if yes you aggreed to some fb app to change your status.....

if no and the status also changes in the new acc... then you should scan your pc.... i recommend spybot, nod 32, and malwarebytes antimalware.....

g luck....