niftyb wrote:
...i just went to check facebook again, and found that i needed to log in... thinking this was strange, i checked my account login activity only to find that i'd been signed on at another location in the house on a nokia mobile phone, and about 10 mins later, windows laptop... 
i'm suspicious that he's either gotten my password from using my laptop, or from my old nokia phone i leant to him because his is on the blink.........
fb on your phone saves your log in details so he might just have logged in by mistake on there, how long was he logged in for? As for on your laptop, he probably logged you out to log himself in and then logged himself in, meaning that you had to log in to get back on, if he had your password he would have been able to log back in as you and you would never have known that someone else had been on it.
I would be tempted to put a password on my laptop if I was you so that he cant use it without asking permission.
He sounds very immature to me, maybe you need to speak to him properly about this, it is not acceptable to use other peoples stuff just because you share a house with them, he is not at home with his family now, it might have been ok for him to use a siblings things but not a housemates.