Help with a job interview?

I have been on several job interviews for banks and loan companys. (I have another interview coming up on thursday). I am very confident and dress well, i keep good eye contact, and i answer the questions in the most detail as possible. Im always early and well mannered. I may get a little nervous, but i try not to show it. The intreviewer always gives me the inpression that i am going to get the job, but they never call me back. I NEED HELP? What am i doing wrong?