Annoyed with my brother in law -i live in his house?

Here is MY problems: I'm living under his roof, but i do pay rent. Room has no door.

(Moving out is not an option)

Here is HIS problems: Sister is pregnant, currently unemployed(probably not for long) Basicly he has too much spare time.

He's always in my bedroom laying on my bed, trying to steal my computer from me whenever i leave the room.

Its not that i dislike having company, its that he's always in here. When i come home from work everyday, i only have 10 hours left to sleep or do some other stuff. I hope you all understand me and can relate, before all the last few hours of the day i rather be left alone, in solitary, just being able to relax and do whatever i want. I just can't take it anymore and ive been having sudden outbursts with him lately, sometimes he just annoys me so much, that i lose all control of myself. He also calls me alot of names, and never does anything he promises, unless its extremely important. I realize that most of the time he may be just joking around with me, but he's always joking around, to the point i can no longer tell whether he's joking or being serious.

Honestly every time he's in my room i always feel uncomfortable like someone is watching over me 24/7, i feel restricted in movement and in space, like i can't even lay down on my own bed whenever i want to because he's always there.

Also i can't simply just talk to him or force him to go out, as im living under his roof, nor will he ever listen to what i really have to say. Every time i try to ask him to leave, he always refuses in a contemptuous tone which really sets me off so i sometimes yell at him for not giving me any space or respect. The worst part is everytime i yell at him i feel horrible about it, like i owe him something. So i'm usually extra nice to him after the outbursts. which just causes the whole cycle to repeat all over again.

He's not a total *******, he just sometimes is. He's a good person overall but i just have trouble with him spending so much time in my room. Maybe he's used to this( he has a brother) but i grew up in a family with 3 sisters so we usually all keep ourselves in our respected boundaries.

Really im desperate right now, to the point im posting my personal problems on yahoo forums.