My adviser is hesistant about letting me graduate. How should I handle it?

I have seen the work of previous and current students and I have done a lot more than them, and my dissertations is about 60% written already, however, my adviser seems to not be comfortable with the idea of me graduating in May (Is January now). I have asked him several times up front and he keeps evading the topic and goes around it and never confirms it. He is always on travel and is not even at my same institution anymore, so that makes things worse. I have a job lined up and he knows about it, but he seems to be holding me back. I have talked to fellow students and they feel he is being unfair to me. What should I do?