Why does he want to know everything about me?

My guy friend who's also my roommate always wants to know where I'm going, what I'm doing, who's calling or texting me, when I'm finishing work etc. He also wants to know who's interested in me, what they look like and what they do. When I tell him about any guys who are interested in me, he sounds annoyed, won't look at me and/or walks off in a huff. To me this is weird because he has a girlfriend. When anyone else is around he acts completely different. Why is this? Is he jealous or something? I tell him that it's my business what I do and I don't ask him what he does! I'm interested in others opinions on this, thanks in advance.